store for loop outcomes in matrix

Hi,

I'm struggling to store for loop outcome in matrix.

for x=33:0.5:35
    %Then I write codes for fitting a mathematical model to a graph using x values of 0 to x to obtain parameters 1-5
    f1= %code for fitting graph
  %And then I write codes for calculating parameter 6
  parameter 6 = blah blah 
  
 %For My final output inside the loop, I wrote:
       output = [x f1.parameter1 f1.parameter2 f1.parameter3 f1.parameter4 f1.parameter5 parameter6] 
       %Parameter1-5 is extracted from 
end

So the final outcome from the loop gives one row with 7 columns

I would like to store my data from my for loop in a matrix so that everytime it produces new output it puts it in the next row.

(So for x=33:0.5:35, it should give a matrix with 5 rows and 7 columns)

How can I acheive this?

Many thanks in advance

Answer 1

[Stephen Cobeldick]

With MATLAB it is generally much better to loop over indices (rather than over data values), then you can simply use those indices for accessing/storing data as required:

V = 33:0.5:35;
N = numel(V);
C = cell(1,N);
for k = 1:N
    x = V(k);
    ... your code
    C{k} = output;
end
M = vertcat(C{:}) % concatenate all vectors into one matrix

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

[Yeeun Son]

thank you so much!

Answer 2

[Andy]

y=1;
for x=33:0.5:35
    %Then I write codes for fitting a mathematical model to a graph using x values of 0 to x to obtain parameters 1-5
    f1= %code for fitting graph
  %And then I write codes for calculating parameter 6
  parameter 6 = blah blah 
  
 %For My final output inside the loop, I wrote:
       output(y,:) = [x f1.parameter1 f1.parameter2 f1.parameter3 f1.parameter4 f1.parameter5 parameter6] 
       %Parameter1-5 is extracted from 
       y=y+1;
end

[Stephen Cobeldick]

To avoid potential bugs and inefficiency, output should be preallocated before the loop:

https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html