Replace values on a column filtering with a value

Hi,

i have a matrix with 56 columns and want to replace with NaN values on a column N corresponding to positions on another column M containing values > of a threshold.

Let's say: if the i-th value of the column 56 is greater than threshold, replace the i-th value of the column N with NaN.

Logical indexing would be better.

Doing this i'm selecting the values greater than 8 on the columns, erasing the others.

R_mod=R(R(:, 56) > 8.0, :)

Thanks in advance,

Alessandro

Answer 1

[Mathieu NOE]

hello

something like that :

%% some dummy data
A = (1:10);
In_Matrix =A'*A;

%% main code %%
Out_Matrix = In_Matrix;

threshold = 45;

col_index_to_test = 9;     % column index where you do the test  > threshold
col_index_to_replace = 8;  % column indexwhere you want to replace values by NaN

ind = find(In_Matrix(:,col_index_to_test) > threshold);
Out_Matrix(ind,col_index_to_replace) = NaN;

Answer 2

[Daniel Catton]

I think I understand what you mean, this works for my understanding of your problem but let me know if I have misunderstood. The user will input their values of 'YourMatrix', 'M' and 'N' and the script will output your 'NewMatrix'.

YourMatrix = ;
M = ;
N = ;

[x,y] = size(YourMatrix);
NewMatrix = YourMatrix;
for i = 1:x
    j = YourMatrix(i,M);
    if j <= 8
        NewMatrix(i,N) = NaN;
    end
end