# Create a new matrix to apply a function

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Miguel Albuquerque on 10 Jun 2022
Answered: Ganesh Gudipati on 15 Jun 2022
I have a matrix range_compression(2032 x 400). For each column of that matrix I want to apply a function(freq2time).This function transforms a vector in frequency domain to a vector in time domain. So I need to apply this function in this matrix, so first, I need to save each column of range_compression matrix and apply the function for all the columns.
And I want that after the apllication of the function for each column of range_compression, it saves the variable range_compressed, column by column in another matrix.
How can I do this, thank you
Range_compression=surv_matrix.*conj(ref_matrix);
[time_rc,Range_compressed]=freq2time(Range_compression,doppler_freqSurv);
dpb on 10 Jun 2022
Well, did you even try the vector approach first?
Have you even tried to address an array column using the <colon, :> operator as illustrated in the Array Indexing section of the <help/matlab/getting-started-with-matlab> guide in the local/online documentation?
If you are as yet so unfamiliar with basic MATLAB syntax, I'd suggest the time invested in the OnRamp tutorials @<Tutorials/matlab-onramp> will more than pay back.

Ganesh Gudipati on 15 Jun 2022
Hi Miguel,
As per my understanding you have a matrix and a function. The function actually process on each column of the matrix and the resultant column will be stored in a different matrix.
The general MATLAB operations used to deal with matrices are attached below
Range_compression(i,j); % to access a cell where row=i and column=j
Range_compression(i,:); % to access all cells where row=i;
Range_compression(:,j); % to access all cells where column=j;
size(Range_compression,1); % gives no of rows in Range_compression
size(Range_compression,2); % gives no of columns in Range_compression
Now you can use a for loop to iterate through all the columns and call freq2time inside the for loop
for j = 1:size(Range_compression,2)
temp = freq2time(Range_compression(:,j))
Range_compressed = [Range_compressed,temp] % appending the column
end

R2021b

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