Search Results

Search found 10060 results on 403 pages for 'column'.

Page 6/403 | < Previous Page | 2 3 4 5 6 7 8 9 10 11 12 13  | Next Page >

  • SQL Server Column Level Encryption - Rotating Keys

    - by BarDev
    We are thinking about using SQL Server Column (cell) Level Encryption for sensitive data. There should be no problem when we initially encryption the column, but we have requirements that every year the Encryption Key needs to change. It seems that this requirement may be problem. Assumption: The table that includes the column that has sensitive data will have 500 million records. Below are the steps we have thought about implementing. During the encryption/decryption process is the data online, and also how long would this process take? Initially encrypt the column New Year Decrypt the column Encrypt the column with new key. Question : When the column is being decrypted/encrypted is the data online (available to be query)? Does SQL Server provide feature that allows for key changes while the data is online? BarDev

    Read the article

  • SQLAuthority News – Follow up on – Replace a Column Name in Multiple Stored Procedure all together

    - by pinaldave
    Last month I had a fantastic time with lots of puzzles and brain teasers, the amount of participation which I have received on the blog is indeed inspiring to write more. One of the blog post was about how to replace a column name in all the stored procedures. The article had very interesting conversation as a follow up. Please read the original article Replace a Column Name in Multiple Stored Procedure all together before reading this blog further as they are connected. Let us start few of the interesting comments. SQL Server Expert Imran Mohammed had a wonderful first and excellent note. I suggest all of you to read it. Imran stresses on the Data Modelling and Logical as well as Physical Design. Developers must create a logical design and get approval on naming convention, data types, references, constraints, indexes etc. He further suggested that one should not cut steps but must follow all the industry standards and guidelines. Here extended my blog post with following note – “Extending Pinal’s answer, what you can do is go to database properties, all tasks, scripts objects, in scripting wizard select all the stored procedure for which you want to change column name, export the query to a new window and then do find and replace, all in once window and execute the script. But make sure you check what you are replacing, sometimes column names are also used in table names, for ex:Table Name: Product and Column Name: ProductId, ProductName”. Thanks Imran Great Points!  Gatej Alexandru suggested that it is not good idea to DROP or CREATE but rather use ALTER as quite possible there may be permissions issue as well. Very good point let me see if I can write blog post over it. Vinay Kumar and SQLStudent144 have proposed another method to achieve the same. I am combining their solution and writing them here. Step 1. Press Ctrl+T or change “Result to Text” mode. Step 2. Execute below commands.SELECT 'EXEC sp_helptext [' + referencing_schema_name + '.' + referencing_entity_name + ']' FROM sys.dm_sql_referencing_entities('schema.objectname','OBJECT') Where schema.objectname is the object or table you are searching for. Step 3. Now copy the result and paste in new window. Again Press Ctrl+T or change “Result to Text” mode. Step 4. Copy the result and paste in new window. Execute the query. Step 5. Copy the result and paste in new window. Step 6. Now find your searching text in the script, make necessary changes and execute this script. Do not forget to remove the code which is generated in resultset which are not relevant to the T-SQL Script. Digitqr suggest we can do this for other objects besides Stored Procedure as well. Iosif suggests to use tool SQL Search from RedGate. I guess this sums it well. We have an alternative perspective to our original issue of replacing the column name in multiple stored procedure. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

    Read the article

  • SQL SERVER – A Puzzle – Swap Value of Column Without Case Statement

    - by pinaldave
    For the last few weeks, I have been doing Friday Puzzles and I am really loving it. Yesterday I received a very interesting question by Navneet Chaurasia on Facebook Page. He was asked this question in one of the interview questions for job. Please read the original thread for a complete idea of the conversation. I am presenting the same question here. Puzzle Let us assume there is a single column in the table called Gender. The challenge is to write a single update statement which will flip or swap the value in the column. For example if the value in the gender column is ‘male’ swap it with ‘female’ and if the value is ‘female’ swap it with ‘male’. Here is the quick setup script for the puzzle. USE tempdb GO CREATE TABLE SimpleTable (ID INT, Gender VARCHAR(10)) GO INSERT INTO SimpleTable (ID, Gender) SELECT 1, 'female' UNION ALL SELECT 2, 'male' UNION ALL SELECT 3, 'male' GO SELECT * FROM SimpleTable GO The above query will return following result set. The puzzle was to write a single update column which will generate following result set. There are multiple answers to this simple puzzle. Let me show you three different ways. I am assuming that the column will have either value ‘male’ or ‘female’ only. Method 1: Using CASE Statement I believe this is going to be the most popular solution as we are all familiar with CASE Statement. UPDATE SimpleTable SET Gender = CASE Gender WHEN 'male' THEN 'female' ELSE 'male' END GO SELECT * FROM SimpleTable GO Method 2: Using REPLACE  Function I totally understand it is the not cleanest solution but it will for sure work in giving situation. UPDATE SimpleTable SET Gender = REPLACE(('fe'+Gender),'fefe','') GO SELECT * FROM SimpleTable GO Method 3: Using IIF in SQL Server 2012 If you are using SQL Server 2012 you can use IIF and get the same effect as CASE statement. UPDATE SimpleTable SET Gender = IIF(Gender = 'male', 'female', 'male') GO SELECT * FROM SimpleTable GO You can read my article series on SQL Server 2012 various functions over here. SQL SERVER – Denali – Logical Function – IIF() – A Quick Introduction SQL SERVER – Detecting Leap Year in T-SQL using SQL Server 2012 – IIF, EOMONTH and CONCAT Function Let us clean up. DROP TABLE SimpleTable GO Question to you: I came up with three simple tricks where there is a single UPDATE statement which swaps the values in the column. Do you know any other simple trick? If yes, please post here in the comments. I will pick two random winners from all the valid answers. Winners will get 1) Print Copy of SQL Server Interview Questions and Answers 2) Free Learning Code for Online Video Courses I will announce the winners on coming Monday. Reference:  Pinal Dave (http://blog.SQLAuthority.com) Filed under: CodeProject, PostADay, SQL, SQL Authority, SQL Interview Questions and Answers, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

    Read the article

  • Enable Multi-Column Google Searches with a User Script

    - by Asian Angel
    Are you wanting to improve the search results view at Google and make better use of the webpage space? With a little user script magic you can make those search results look and fit better in your favorite browser. Note: This user script may conflict with the AutoPager extension if you have it installed in your favorite browser. Before Here is the standard single column view of search results at Google. Not too bad but the available space could certainly be better utilized. Note: For the purposes of our example we are using Google Chrome but this user script can be easily added to other browsers. After If you have never installed a user script in Chrome before it is just as simple as the regular extensions at the official Google website. Here you can see the details for the user script we are installing. Notice that you can view the source code if desired. To add the user script to Chrome click on “Install”. Once you start the install process you will see an intermediary message asking if you wish to continue in the lower left corner of your browser. Click “Continue” to move to the next step in the install process. From this point on the install process is practically identical to the official extensions. You can see the final confirmation window here…click “Install” to finish adding the user script to Chrome. As with regular extensions you will see a post-install message in the upper right corner. So, what does a user script look like in the “Extensions Page”? You can see the user script entry here…outside of an icon it looks rather identical to a normal extension. After refreshing the search page shown above we now have two columns of search results (default setting). This looks much much better than a single column view and there is little to no page scrolling required now. To switch to a three column view simply use the keyboard shortcut “Alt + 3”. To return to a single column view use “Alt + 1” and for the default two column view use “Alt + 2”. Three keyboard shortcuts for three different views…definitely a good thing. Note: On our test system we needed to use the number keys at the top of our keyboard to switch views…this is most likely the result of unique settings on our test system. Conclusion If you are wanting a better viewing experience when conducting searches at Google then this user script will make a very nice addition to your favorite browser. For those using Firefox you can add user scripts with the Greasemonkey & Stylish extensions. Using Opera Browser? See our how-to for adding user scripts to Opera here. Links Install the Multi-Column View of Google Search Results User Script Similar Articles Productive Geek Tips Hide Flash Animations in Google ChromeEnable Google Search From Shortcut Key in KDE on (k)UbuntuSet Gmail as Default Mail Client in UbuntuSet Up User Scripts in Opera BrowserHow To Enable Favicons for Google Reader Subscriptions TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Yes, it’s Patch Tuesday Generate Stunning Tag Clouds With Tagxedo Install, Remove and HIDE Fonts in Windows 7 Need Help with Your Home Network? Awesome Lyrics Finder for Winamp & Windows Media Player Download Videos from Hulu

    Read the article

  • What does the length attribute do when set on the @Column JPA annontation?

    - by James McMahon
    What exactly does setting the length on a column do in JPA? @Column(name = "middle_name", nullable = false, length = 32) public String getMiddleName() { return this.middleName; } I understand that you can use the annotations to generate the database schema based on the entity objects, but does length do any sort of check or truncation when persistence happens, or it solely used for schema creation? I also realize that JPA can sit on top of various implementations, the implementation I am concerned with in this case, is Hibernate.

    Read the article

  • Excel Issues macro may be needed

    - by user124643
    I trying to compare lists in excel. There are two lists, one list just has one column and the other has two columns, and what I am trying to do is when column A matches column C than take the value in column D and use that to replace column A. For example: Column A Column B Column C Column D Blue Blue Shirt Blue Red Pants Red Green Shoes Red Green Green Purple So the completed list should look like: Column A Column B Column C Column D Shirt Blue Shirt Shirt Red Pants Pants Green Shoes Pants Shoes Shoes Purple

    Read the article

  • Windows 7: Add column to ALL music folders

    - by Joel Spolsky
    In Windows 7 Explorer, when I open a folder containing only music, it's smart enough to show me a custom set of columns (Name, #, Title, Contributing Artists, Album) that make sense for a music folder. However, I also always want to see a Length column. I can right click on the column headers and add the Length column, which is persistent for that folder, but when I go to another music folder, it doesn't have the new Length column. How do I set up Windows so that ALL music folders ALWAYS show me this column?

    Read the article

  • Column break in word - continously

    - by Holian
    Masters, I need to PASTE my content in two different column in word. (I have 300 page of old content and 300 page of new content, i want to share my partners this information side by side to compare) I made two column and instert a column break, but i have to insert column break every page? How can i do this easier? Any way to insert column break continously, so i just need to copy&paste the contents into the columns? thank you

    Read the article

  • Convert a Row to a Column in Excel the Easy Way

    - by Matthew Guay
    Sometimes we’ve entered data in a column in Excel, only to realize later that it would be better to have this data in a row, or vise-versa.  Here’s a simple trick to convert any row or set of rows into a column, or vise-versa, in Excel. Please Note: This is tested in Excel 2003, 2007, and 2010.  Here we took screenshots from Excel 2010 x64, but it works the same on the other versions. Convert a Row to a Column Here’s our data in Excel: We want to change these two columns into rows.  Select all the cells you wish to convert, right-click, and select copy (or simply press Ctrl+C): Now, right-click in the cell where you want to put the data in rows, and select “Paste Special…”   Check the box at the bottom that says “Transpose”, and then click OK. Now your data that was in columns is in rows! This works the exact same for converting rows into columns.  Here’s some data in rows:   After copying and pasting special with Transpose selected, here’s the data in columns! This is a great way to get your data organized just like you want in Excel. Similar Articles Productive Geek Tips Convert Older Excel Documents to Excel 2007 FormatHow To Import a CSV File Containing a Column With a Leading 0 Into ExcelExport an Access 2003 Report Into Excel SpreadsheetMake Row Labels In Excel 2007 Freeze For Easier ReadingKeyboard Ninja: Insert Tables in Word 2007 TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 PCmover Professional Increase the size of Taskbar Previews (Win 7) Scan your PC for nasties with Panda ActiveScan CleanMem – Memory Cleaner AceStock – The Personal Stock Monitor Add Multiple Tabs to Office Programs The Wearing of the Green – St. Patrick’s Day Theme (Firefox)

    Read the article

  • Document-oriented vs Column-oriented database fit

    - by user1007922
    I have a data-intensive application that desperately needs a database make-over. The general data model: There are records with RIDs, grouped together by group IDs (GID). The records have arbitrary data fields, (maybe 5-15) with a few of them mandatory and the rest optional, and thus sparse. The general use model: There are LOTS and LOTS of Writes. Millions to Billions of records are stored. Very often, they are associated with new GIDs, but sometimes, they are associated with existing GIDs. There aren't as many reads, but when they happen, they need to be pretty fast or at least constant speed regardless of the database size. And when the reads happen, it will need to retrieve all the records/RIDs with a certain GID. I don't have a need to search by the record field values. Primarily, I will need to query by the GID and maybe RID. What database implementation should I use? I did some initial research between document-oriented and column-oriented databases and it seems the document-oriented ones are a good fit, model-wise. I could store all the records together under the same document key using the GID. But I don't really have any use for their ability to search the document contents itself. I like the simplicity and scalability of column-oriented databases like Cassandra, but how should I model my data in this paradigm for optimal performance? Should my key be the GID and should I create a column for each record/RID? (there maybe thousands or hundreds of thousands of records in a group/GID). Or should my key be the RID and ensure each row has a column for the GID value? What results in faster writes and reads under this model?

    Read the article

  • MySQL – Grouping by Multiple Columns to Single Column as A String

    - by Pinal Dave
    In this post titled SQL SERVER – Grouping by Multiple Columns to Single Column as A String we have seen how to group multiple column data in comma separate values in a single row grouping by another column by using FOR XML clause. In this post we will see how we can produce the same result using the GROUP_CONCAT function in MySQL. Let us create the following table and data. CREATE TABLE TestTable (ID INT, Col VARCHAR(4)); INSERT INTO TestTable (ID, Col) SELECT 1, 'A' UNION ALL SELECT 1, 'B' UNION ALL SELECT 1, 'C' UNION ALL SELECT 2, 'A' UNION ALL SELECT 2, 'B' UNION ALL SELECT 2, 'C' UNION ALL SELECT 2, 'D' UNION ALL SELECT 2, 'E'; Now to generate csv values of the column col for each ID, use the following code SELECT ID, GROUP_CONCAT(col) AS CSV FROM TestTable GROUP BY ID; The result is ID CSV 1 A,B,C 2 A,B,C,D,E You can also change the delimiters. For example instead of comma, if you want to have a pipe symbol (|), use the following SELECT ID, REPLACE(GROUP_CONCAT(col),',','|') AS CSV FROM TestTable GROUP BY ID; The result is ID CSV 1 A|B|C 2 A|B|C|D|E MySQL makes this very simple with its support of GROUP_CONCAT function. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

    Read the article

  • SQL SERVER – Grouping by Multiple Columns to Single Column as A String

    - by pinaldave
    One of the most common questions I receive in email is how to group multiple column data in comma separate values in a single row grouping by another column. I have previously blogged about it in following two blog posts. However, both aren’t addressing the following exact problem. Comma Separated Values (CSV) from Table Column Comma Separated Values (CSV) from Table Column – Part 2 The question comes in many different formats but in following image I am demonstrating the same question in simple words. This is the most popular question on my Facebook page as well. (Example) Here is the sample script to build the sample dataset. CREATE TABLE TestTable (ID INT, Col VARCHAR(4)) GO INSERT INTO TestTable (ID, Col) SELECT 1, 'A' UNION ALL SELECT 1, 'B' UNION ALL SELECT 1, 'C' UNION ALL SELECT 2, 'A' UNION ALL SELECT 2, 'B' UNION ALL SELECT 2, 'C' UNION ALL SELECT 2, 'D' UNION ALL SELECT 2, 'E' GO SELECT * FROM TestTable GO Here is the solution which will build an answer to the above question. -- Get CSV values SELECT t.ID, STUFF( (SELECT ',' + s.Col FROM TestTable s WHERE s.ID = t.ID FOR XML PATH('')),1,1,'') AS CSV FROM TestTable AS t GROUP BY t.ID GO I hope this is an easy solution. I am going to point to this blog post in the future for all the similar questions. Final Clean Up Act -- Clean up DROP TABLE TestTable GO Here is the question back to you - Is there any better way to write above script? Please leave a comment and I will write a separate blog post with due credit. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL XML

    Read the article

  • Overlap of the variable in mysql, my column are set to my query result

    - by foodil
    The question is not clear , let me clarify it: try{ $sql = ' SELECT UserID <==== (***********Used here for query ******) FROM user WHERE Rights != ?'; $stmt = $conn->prepare($sql); $stmt->execute(array('admin')); $result= $stmt->fetchAll(); } catch(PDOException $e) { die ($e->getMessage().'<a href="add.php"> Back</a>'); } foreach ($result as $set) { if ($set['UserID']==$_SESSION['username']) $rights='edit'; else {$rights=$_POST[$set['UserID']];} if (($rights != 'default' || $set['UserID']==$_SESSION['username']) && $_POST['public']==0 ) { $user=$set['UserID']; try { $query="INSERT INTO user_list(UserID <==== (***********Used here for insert ******),ListID,UserRights) VALUES ($user,$lastID,$rights)"; $stmt = $conn->prepare($query); $stmt->execute(); } catch(PDOException $e) { die ($e->getMessage().'<a href="add.php"> Back</a>'); $conn->rollBack(); } } } As you can see the UserID is a query result but it is also the column i need to insert, so when i insert into the table it will casued an error SQLSTATE[42S22]: Column not found: 1054 Unknown column 'UserA_ID' in 'field list' because the column is modify by my query result from: $query="INSERT INTO user_list(UserID,ListID,UserRights) VALUES ($user,$lastID,$rights)"; to: $query="INSERT INTO user_list(query_result_id,ListID,UserRights) VALUES ($user,$lastID,$rights)"; How to fix it ?Thank you.

    Read the article

  • How can I factor out repeated expressions in an SQL Query? Column aliases don't seem to be the ticke

    - by Weston C
    So, I've got a query that looks something like this: SELECT id, DATE_FORMAT(CONVERT_TZ(callTime,'+0:00','-7:00'),'%b %d %Y') as callDate, DATE_FORMAT(CONVERT_TZ(callTime,'+0:00','-7:00'),'%H:%i') as callTimeOfDay, SEC_TO_TIME(callLength) as callLength FROM cs_calldata WHERE customerCode='999999-abc-blahblahblah' AND CONVERT_TZ(callTime,'+0:00','-7:00') >= '2010-04-25' AND CONVERT_TZ(callTime,'+0:00','-7:00') <= '2010-05-25' If you're like me, you probably start thinking that maybe it would improve readability and possibly the performance of this query if I wasn't asking it to compute CONVERT_TZ(callTime,'+0:00','-7:00') four separate times. So I try to create a column alias for that expression and replace further occurances with that alias: SELECT id, CONVERT_TZ(callTime,'+0:00','-7:00') as callTimeZoned, DATE_FORMAT(callTimeZoned,'%b %d %Y') as callDate, DATE_FORMAT(callTimeZoned,'%H:%i') as callTimeOfDay, SEC_TO_TIME(callLength) as callLength FROM cs_calldata WHERE customerCode='5999999-abc-blahblahblah' AND callTimeZoned >= '2010-04-25' AND callTimeZoned <= '2010-05-25' This is when I learned, to quote the MySQL manual: Standard SQL disallows references to column aliases in a WHERE clause. This restriction is imposed because when the WHERE clause is evaluated, the column value may not yet have been determined. So, that approach would seem to be dead in the water. How is someone writing queries with recurring expressions like this supposed to deal with it?

    Read the article

  • How do I select column(s) by their "numeric" position in a table?

    - by DulcimerDude
    I am trying to select columns by their "x" position in the table. DBI my $example = $hookup->prepare(qq{SELECT This,That,Condition,"I also want COLUMN-10" FROM tbl LIMIT ? ?}); ###column_number=10 ordinal_position?? $example->execute('2','10') or die "Did not execute"; Is this possible or do I need to run another single select to just that column? One problem I encountered was with a col named "Condition". For some reason, when I tried to select Condition the execute would die. I never attempted but, What if the column name was SELECT? Another note is the table is 75 cols wide and I only need 50 of them. The Col names are pretty verbose so, I would like to just call them by their "position". This would also allow the col names to be changed in the future without having to change the select statement. I am quite the newbie so please explain any answers down to my level. Thanks for any assistance..

    Read the article

  • Instead of alter table column to turn IDENTITY on and off, turn IDENTITY_INSERT on and off

    - by Kevin Shyr
    First of all, I don't know which version of SQL this post (http://www.techonthenet.com/sql/tables/alter_table.php) is based on, but at least for Microsoft SQL Server 2008, the syntax is not: ALTER TABLE [table_name] MODIFY [column_name] [data_type] NOT NULL; Instead, it should be: ALTER TABLE [table_name] ALTER COLUMN [column_name] [data_type] NOT NULL;   Then, as several posts point out, you can't use T-SQL to run an existing column into an IDENTITY column.  Instead, use the IDENTITY_INSERT to copy data from other tables.  http://msdn.microsoft.com/en-us/library/ms188059.aspx SET IDENTITY_INSERT [table_name] ON INSERT .... SET IDENTITY_INSERT [table_name] OFF     http://www.sqlservercentral.com/Forums/Topic126147-8-1.aspx http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=65257

    Read the article

  • Why is prefixing column names considered bad practice?

    - by P.Brian.Mackey
    According to a popular SO post is it considered a bad practice to prefix table names. At my company every column is prefixed by a table name. This is difficult for me to read. I'm not sure the reason, but this naming is actually the company standard. I can't stand the naming convention, but I have no documentation to back up my reasoning. All I know is that reading AdventureWorks is much simpler. In this our company DB you will see a table, Person and it might have column name: Person_First_Name or maybe even Person_Person_First_Name (don't ask me why you see person 2x) Why is it considered a bad practice to pre-fix column names? Are underscores considered evil in SQL as well? Note: I own Pro SQL Server 2008 - Relation Database design and implementation. References to that book are welcome.

    Read the article

  • Visual C++, CMap object save to blob column

    - by ilansch
    I have a MFC CMap object, each object stores 160K~ entries of long data. I need to store it on Oracle SQL. we decided to save it as a blob. since we do not want to make additional table. we also thought about saving it as local file and point the SQL column to that file, but we rather just keep it as blob on the server and clear the table every couple of weeks. The table has a sequential key as ID, and 2 column of time. I need to add the blob column in order to store on every row that CMap. Can you recommend a guide to do so (read/write Map to blob or maybe a clob) ? Thanks.

    Read the article

  • Word 2010, Multiple Columns, Vertical center one column only

    - by Nancy N Jones
    I am creating a document with two columns in Microsoft Word 2010. I want the first column to be centered vertically. I want the second column to be on the same page and the vertical placement to be from the top. I highlight my text in the first column that I want centered vertically, then go to Page Layout Margins Custom Margins Layout, you can choose to center the vertical alignment. I have choosen the "Section Start" to be "Column" and also tried "Continuous." In all cases it always shifts all of my second column information to a new page. I don't want my second column text to be on a new page, I want it to be on the same page and vertically aligned from the top--not the center. Am I understanding the functionality of the Section Start on the Layout tab correctly? Maybe the page layout isn't the correct formatting to use. What I am really doing is formatting columns. I haven't found anywhere to format the columns for this. Am I missing some important column formatting features? I know that I can use the paragraph formatting and add space above the first line of text to make it look like it is centered vertically. However, this is a template for a master document and will be changed frequently. I really would like the first column text to be automatically formatted to be centered vertically without having to go in and manually change the space above the paragraph every time. Your assistance would be greatly appreciated.

    Read the article

  • Pass a data.frame column name to a function

    - by Kevin Middleton
    I'm trying to write a function to accept a data.frame (x) and a column from it. The function performs some calculations on x and later returns another data.frame. I'm stuck on the best-practices method to pass the column name to the function. The two minimal examples fun1 and fun2 below produce the desired result, being able to perform operations on x$column, using max() as an example. However, both rely on the seemingly (at least to me) inelegant (1) call to substitute() and possibly eval() and (2) the need to pass the column name as a character vector. fun1 <- function(x, column){ do.call("max", list(substitute(x[a], list(a = column)))) } fun2 <- function(x, column){ max(eval((substitute(x[a], list(a = column))))) } df <- data.frame(A = 1:20, B = rnorm(10)) fun1(df, "B") fun2(df, "B") I would like to be able to call the function as fun(df, B), for example. Other options I have considered but have not tried: Pass column as an integer of the column number. I think this would avoid substitute(). Ideally, the function could accept either. with(x, get(column)), but, even if it works, I think this would still require substitute Make use of formula() and match.call(), neither of which I have much experience with. Subquestion: Is do.call() preferred over eval()? Thanks, Kevin

    Read the article

< Previous Page | 2 3 4 5 6 7 8 9 10 11 12 13  | Next Page >