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  • Help me understand FFT function (Matlab)

    - by estourodepilha.com
    1) Besides the negative frequencies, which is the minimum frequency provided by the FFT function? Is it zero? 2) If it is zero how do we plot zero on a logarithmic scale? 3) The result is always symmetrical? Or it just appears to be symmetrical? 4) If I use abs(fft(y)) to compare 2 signals, may I lose some accuracy?

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  • Return popupmenu selection in MATLAB using one line of code

    - by Doresoom
    I have a GUI which uses a selection from a popupmenu in another callback. Is there a way to return the selected value of the popupmenu in only one line without creating any temporary variables? I've tried several solutions, but I've only managed two lines with one temporary variable: Three lines: list=get(handles.popupmenu1,'String'); val=get(handles.popupmenu1,'Value'); str=list{val}; Two lines: temp=get(handles.popupmenu1,{'String','Value'}); str=temp{1}{temp{2}}; Can anyone shave it down to one? PS, It's a dynamic menu, so I can't just use get(handles.popupmenu1,'Value') and ignore the string component altogether.)

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  • Extracting data points from a matrix and saving them in different matrixes in MATLAB

    - by Hossein
    Hi, I have a 2D Matrix consisting of some coordinates as below(example): Data(X,Y): 45.987543423,5.35000964 52.987544223,5,98765234 Also I have an array consisting of some integers =0 , for example: Cluster(M) 2,0,3,1 each of these numbers in this array corresponds with a row of my 2D Matrix above.For example, it says that row one(coordinate) in the Data Matirx belongs to the cluster 2,second row belongs to cluster 0 and so on. Now I want to have each of the datapoint of each cluster in a separate matrix, for example I want to save datapoints belonging to cluster 1 in a separate matrix, cluster 2 in a separate matrix and so on,.... I can do them manually, but the problem is this has to be an automatic extraction. which means that the number of clusters(range of the numbers in the cluster array varies in each run) so I have to have a general algorithm that does this extraction for me. Can someone help me please? thanks

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  • Calculate area under FFT graph in Matlab

    - by lytheone
    Hiya, Currently I did a FFT of a set of data which gives me a plot with frequency at x axis and amplitude at y axis. I would like to calculate out the area under graph to give me energy. I am not sure how to determinate the area because i am without the equation and also i only want a certain area of the plot rather than whole area under the plot. Is there a way i can do it?

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  • summing functions handles in matlab

    - by user552231
    Hi I am trying to sum two function handles, but it doesn't work. for example: y1=@(x)(x*x); y2=@(x)(x*x+3*x); y3=y1+y2 The error I receive is "??? Undefined function or method 'plus' for input arguments of type 'function_handle'." This is just a small example, in reality I actually need to iteratively sum about 500 functions that are dependent on each other. EDIT The solution by Clement J. indeed works but I couldn't manage to generalize this into a loop and ran into a problem. I have the function s=@(x,y,z)((1-exp(-x*y)-z)*exp(-x*y)); And I have a vector v that contains 536 data points and another vector w that also contains 536 data points. My goal is to sum up s(v(i),y,w(i)) for i=1...536 Thus getting one function in the variable y which is the sum of 536 functions. The syntax I tried in order to do this is: sum=@(y)(s(v(1),y,z2(1))); for i=2:536 sum=@(y)(sum+s(v(i),y,z2(i))) end

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  • MATLAB: Need to make a 4D plot (3D + Colour/Color)

    - by user1305624
    I need to make a 3D surface where colour will represent the fourth variable. I know "surf" is SIMILAR to what I need, but that's not quite it. Basically, I have the following variables: t = [1:m] y = [1:n] a = [1:o] These should be the three Cartesian corodinate axes. I also have a variable S that is of dimensions m x n x o, and is basically the amplitude, a function of the previous three variables (i.e. S = f(t,y,a)). I want this to be represented by colour. So to summarize, I need a graph of the form (t,y,a,S), where the first three variables are vectors of unequal sizes and the final variable is a multidimensional array whose dimensions are determined by the first three. Thanks in advance.

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  • How to return something in Matlab?

    - by Ben Fossen
    I have a simple function function increase(percent, number) low = number- number*percent; end I want to return low so I can use it as an argument for another function mitoGen(asp, arg, increase(.2,234), glu) Is there a way to do this?

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  • Uniform distribution of binary values in Matlab

    - by JohnIdol
    I have a requirement for the generation of a given number N of vectors of given size each consistent of a uniform distribution of 0s and 1s. This is what I am doing at the moment, but I noticed that the distribution is strongly peaked at half 1s and half 0s, which is no good for what I am doing: a = randint(1, sizeOfVector, [0 1]); The unifrnd function looks promising for what I need, but I can't manage to understand how to output a binary vector of that size. Is it the case that I can use the unifrnd function (and if so how would be appreciated!) or can is there any other more convenient way to obtain such a set of vectors? Any help appreciated!

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  • Reading a text file in MATLAB line by line

    - by Hossein
    Hi, I have a CSV file, I want to read this file and do some pre-calculations on each row to see for example that row is useful for me or not and if yes I save it to a new CSV file. can someone give me an example? in more details this is how my data looks like: (string,float,float) the numbers are coordinates. ABC,51.9358183333333,4.183255 ABC,51.9353866666667,4.1841 ABC,51.9351716666667,4.184565 ABC,51.9343083333333,4.186425 ABC,51.9343083333333,4.186425 ABC,51.9340916666667,4.18688333333333 basically i want to save the rows that have for distances more than 50 or 50 in a new file.the string field should also be copied. thanks

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  • invalid file name in matlab when using file split

    - by klijo
    here jj will be the value of FN, but the trouble is iam getting a error message ??? Error using == fopen Invalid filename. DirName = 'Samples\mattest\jj'; FileName = split('\\',DirName); [a,b] = size(FileName); FN = FileName(b); file_1 = fopen(FN,'w'); split method was found at http://www.mathworks.com/matlabcentral/fileexchange/4873 Doesnt the code seem correct ? Could someone please help me ?

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  • Matlab Correlation Function

    - by Joka
    function letter=read_char(imgn, num_letters) global templates comp=[ ]; for n=1:num_letters sem=corr2(imgn, templates{1,n}); comp=[comp sem]; end vd=find(comp==max(comp)); Can someon please explain what the 'FOR' loop does and how 'vd' is calculated? Also, what is the variable 'comp' and what will it looks like as the array also contains itself and another variable 'sem' which is calculated from the corr2 function. thanks

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  • set width of bars in matlab bar plot on logarithmic scale

    - by KatyB
    I am a bit confused on how to draw a bar graph for the following example: x_lims = [1000,10000;10000,100000;100000,1000000;1000000,10000000;10000000,... 100000000;100000000,1000000000;1000000000,10000000000;... 10000000000,100000000000;100000000000,1e12]; ex1 = [277422033.049038;24118536.4203188;2096819.03295482;... 182293.402068030;15905;1330;105;16;1]; Here, x_lims is the x axis limits for each individual bar and ex1 is the count. How can I plot these on a bar graph so that the width of each individual bar along the x axis is defined by the distance between x_lims(:,1) and x_lims(:,2) and the y value is defined by ex1? So far I have: bar(log10(x_lims(:,1)),log10(ex1)); set(gca,'Xtick',3:11,'YTick',0:9); set(gca,'Xticklabel',10.^get(gca,'Xtick'),... 'Yticklabel',10.^get(gca,'Ytick')); But I would like to (1) have the labels to be the same as if they were created using semilogx or semilogy e.g. 10^9, and (2) I would like to remove the space between the bars, for the first bar, for example, I would like to have it extend horizontally from 1000 to 10000 and then the second bar from 10000 to 100000, and so on. How can this be done?

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  • check sequence in matlab

    - by gabboshow
    I have a vector that should contain n sequences from 00 to 11 A = [00;01;02;03;04;05;06;07;08;09;10;11;00;01;02;03;04;05;06;07;08;09;10;11] and I would like to check that the sequence "00 - 11 " is always respected (no missing values). for example if A =[00;01;02; 04;05;06;07;08;09;10;11;00;01;02;03;04;05;06;07;08;09;10;11] (missing 03 in the 3rd position) For each missing value I would like to have back this information in another vector missing= [value_1,position_1; value_2, position_2; etc, etc] Can you help me?

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  • Basic FreeMat/MATLAB syntax - dimension error

    - by 0x90
    I am using FreeMat, and I have an RGB picture which is a 3D matrix contains the columns and rows of the pictures and the RGB values for each pixel. Since there is not an intrinsic function to convert RGB picture to YIQ, I have implement one. I came up with this code: Assume I have a 3D array, image_rgb: matrix = [0.299 0.587 0.114; 0.596 -0.274 -0.322; 0.211 -0.523 0.312]; row = 1:length(image_rgb(:,1,1)); col = 1:length(image_rgb(1,:,1)); p = image_rgb(row,col,:); %Here I have the problem mage_yiq(row,col,:) = matrix*image_rgb(row,col,:); max_y = max (max(image_yiq(:,:,1))); max_i = max (max(image_yiq(:,:,2))); max_q = max (max(image_yiq(:,:,3))); %Renormalize the image again after the multipication % to [0,1]. image_yiq(:,:,1) = image_yiq(:,:,1)/max_y; image_yiq(:,:,2) = image_yiq(:,:,2)/max_i; image_yiq(:,:,3) = image_yiq(:,:,3)/max_q; I can't understand why the matrix multiplication fails. I want the code to be nice and not just to, multiply the matrix by hand...

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  • Matlab - Propagate unit vectors on to the edge of shape boundaries

    - by Graham
    Hi I have a set of unit vectors which I want to propagate on to the edge of shape boundary defined by a binary image. The shape boundary is defined by a 1px wide white edge. I also have the coordinates of these points stored in a 2 row by n column matrix. The shape forms a concave boundary with no holes within itself made of around 2500 points. What would be the best method to do this? Are there some sort of ray tracing algorithms that could be used? Or would it be a case of taking the unit vector and multiplying it by a scalar and testing after multiplication if the end point of the vector is outside the shape boundary. When the end point of the unit vector is outside the shape, just find the point of intersection? Thank you very much in advance for any help!

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  • How to Save data in txt file in MATLAB

    - by Jessy
    I have 3 txt files s1.txt, s2.txt, s3.txt.Each have the same format and number of data.I want to combine only the second column of each of the 3 files into one file. Before I combine the data, I sorted it according to the 1st column: UnSorted file: s1.txt s2.txt s3.txt 1 23 2 33 3 22 4 32 4 32 2 11 5 22 1 10 5 28 2 55 8 11 7 11 Sorted file: s1.txt s2.txt s3.txt 1 23 1 10 2 11 2 55 2 33 3 22 4 32 4 32 5 28 5 22 8 11 7 11 Here is the code I have so far: BaseFile ='s' n=3 fid=fopen('RT.txt','w'); for i=1:n %Open each file consecutively d(i)=fopen([BaseFile num2str(i)'.txt']); %read data from file A=textscan(d(i),'%f%f') a=A{1} b=A{2} ab=[a,b]; %sort the data according to the 1st column B=sortrows(ab,1); %delete the 1st column after being sorted B(:,1)=[] %write to a new file fprintf(fid,'%d\n',B'); %close (d(i)); end fclose(fid); How can I get the output in the new txt file in this format? 23 10 11 55 33 22 32 32 28 22 11 11 instead of this format? 23 55 32 22 10 33 32 11 11 22 28 11

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  • Instantaneous frequency not plotting correctly in Matlab

    - by user2951069
    I'm trying to convert square wave data to instantaneous frequency and plot against time. It works correctly for one data set, but three others are plotting as shown in the image: http://i.imgur.com/iuL648o.png Time is linear, so it shouldn't be plotting like that. Anyone have any ideas as to what's going on? I'm using the following code: ddiff = diff(flow(:,1)); locations = find(ddiff(1:end-1,1)>0.1 & ddiff(2:end,1) <=0.1); for z = 2:length(locations) inst_freq(z-1) = 1/(time(locations(z))-time(locations(z-1))); freq_time(z-1) = time(locations(z)); end plot(freq_time,inst_freq)

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