How to find Y value that corresponds to the maximum X value in these graphs?

Hi,

I need to find the Y value that corresponds to the maximum X value for the curves attached herewith.

I tried to use interp1, but I am not sure how to make it for several files.

Can anyone please help me with this?

Thank you.

[Bob Thompson]

Do you have the data for the plots? (There was nothing attached).

If you do have the data this should be fairly easy with logic indexing. I'm going to assume that your data set is two columns, with x in the first column, and y in the second column.

maxy = data(max(data(:,1)),2);

[Ismail Qeshta]

Hi Bob,

Thank you for your comment and suggestion. I have just attached the data.

I just need to find the Y value at maximum X and print the output in a file.

[Bob Thompson]

The little bit of code from my previous comment should find you the y value you are looking for.

[Ismail Qeshta]

Hi Bob,

I tried to develop this code, but it does not work.

I get the following error message:

Index in position 1 is invalid. Array indices must be positive integers or logical values.

Error in ResidualDisp (line 10)

maxy = matDrift(max(matDrift(:,1)),2);

clear; clc;
Folder = cd;
N=10;
for k = 1:N;
  Driftt  = sprintf('X%d.out', k);
  matDrift     = importdata(fullfile(Folder, Driftt));

maxy = matDrift(max(matDrift(:,1)),2);
end

[Stephen23]

See also later question:

https://www.mathworks.com/matlabcentral/answers/445771-how-to-sort-the-results-correctly-in-this-for-loop

Answer 1

[KSSV]

files = dir('*.txt') ;
N = length(files) ;
iwant = zeros(N,2) ;
for i = 1:N
    data = load(files(i).name) ;
    [val,idx] = max(data(:,1)) ;
    iwant(i,:) = [val data(idx,2)] ;
end

[Ismail Qeshta]

Thank you KSSV for suggesting the code. It does not give any results. All columns are empty.

I tried the following code, but I get this error message.

Index in position 1 is invalid. Array indices must be positive integers or logical values.

Error in ResidualDisp (line 10)

maxy = matDrift(max(matDrift(:,1)),2);

clear; clc;
Folder = cd;
N=10;
for k = 1:N;
  Driftt  = sprintf('X%d.out', k);
  matDrift     = importdata(fullfile(Folder, Driftt));
maxy = matDrift(max(matDrift(:,1)),2);
end

[KSSV]

It does not give any results. All columns are empty. No it shall give the results......it depends on how you are using it. Did you run the code in the folder where the text files are present?

[Ismail Qeshta]

Thanks KSSV. Yes, it worked after I changed the format of my files to ".out".

However, the results are 20X2. They should be only 10X2.

I checked the numbers, the first row is correct, while the others are not.

[KSSV]

How many files are there in the folder?

[Ismail Qeshta]

Yes. I have just corrected that. Sorry, I copied similar files name at the same folder.

Now that all the results are in 10X2. However, something still seems to be not working.

For example, the first row is correct. The second one records the 10th one. Then, the rest are recorded sequentially, for example, 3rd row records the 2nd file, 4th row records the 5th file until the 9th file.

[Ismail Qeshta]

I changed the files data to check it further, and I got the same thing.

[KSSV]

Okay.....try this https://in.mathworks.com/matlabcentral/fileexchange/10959-sort_nat-natural-order-sort to read the file sin order.

[Ismail Qeshta]

Hi KSSV,

Thank you for your suggestion.

I am not sure, I have used it as below, but it still does not work.

The updated code:

files = dir('*.out') ;
N = length(files) ;
iwant = zeros(N,2) ;
for i = 1:N
    data = load(files(i).name) ;
    [val,idx] = sort_nat((max(data(:,1))));
    iwant(i,:) =[val data(idx,2)];
end