MATLAB: How to select columns from data matrix using “for” loop

forfor loopinterpolationlooploopsmatrix

Hi,

I would like to select columns from a data matrix and use them to interpolate data from another file. For example, first column is selected and interpolated from another file, and printed, then the second column, and so on. I know the interpolation code, but I need the selection of column and printing the interpolated data codes.

I would be grateful if someone can help me in this.

Thank you. Regards, Ismail

Best Answer

One approach:

for i=1:size(A,2)%number of columns
    b=A(:,i);%ith column is assigned to b variable at every step
    interp(b,..);%you can use it in your function 
end

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Your loop needs to provide an index into x2

x2(something)= interp1(y3, x3, y2, 'linear')

to tell it where to store things.

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The code contains several problems:

1. fullfile(Driftt) does not do anything. Define the directory in addition:

Folder = cd;
...
   matDrift     = importdata(fullfile(Folder, Driftt));

2. Do not use "sort" as name of a variable, because this shadows the important function with the same name. This is not an error directly, but trying to use the function|sort()| afterwards produces unexpected behavior.

3. What is the value of "N"?

Perhaps you want:

    sorted = zeros(N,2);
    for i = 1:N
      [valy, idx] = max(y(i, :));  % or y(:, i)?
      sorted(i,:) = [x(idx,1), valy];
      % hold on;  Completely useless here, remove it
    end

hold set the 'NextPlot' property of the current axes such that following plot commands do not remove existing line objects. But you are nor drawing here.

You could do this without a loop also:

[valy, idx] = max(y, [], 2);  % or max(y, [], 1) ?

sorted      = [x(idx, 1), valy];

Perhaps you have to modify the dimensions for the concatenation.

4. The variable "sort" (renamed to "sorted" in my code) is overwritten. Perhaps you want:

sorted = cell(1, 3);
...
[valy, idx] = max(y, [], 2);  % or max(y, [], 1) ?
sorted{k}   = [x(idx, 1), valy];

Best Answer

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