Finding the first time a number appears in a matrix

I have matrix c and I am looking to find the first time the number 0.7 appears in the matrix searching row by row.

I have this code to search for it in the first row "columnindex=find(c(1,:)>=0.7,1,'first');" but if it does not appear in the first row how do I search the row below and so on?

Thank you.

Answer 1

[Star Strider]

Try this —

c = randi([650 750], 50)*1E-3;                              % Create Matrix

[val,idx] = min(abs(c(:)-0.7))                              % Minimum Of Absolute Difference (Linear Index

val = 1.1102e-16

idx = 94

[crr,ccc] = ind2sub(size(c),idx)                            % Convert To Subscripts

crr = 44

ccc = 2

Check = c(crr,ccc)                                          % Check Result (Delete Later)

Check = 0.7000

.

[Sam Robinson]

This doesn't work fully because I just tried it and had a value of 0.7 in my first row but it had my crr as 12, do you know why this is?

Appreciate your help though

[Star Strider]

My pleasure!

The way llinear indexing works, it should scan the first column, then the second column, and so forth.

Transposing ‘c’ first will likely create the linear index appropriately with respect to the ‘ct(:)’ vector to give the result you want, then reversing ‘crr’ and ‘ccc’ in the ind2sub output —

c = rand(7);                                    % Create Matrix
c(3,5) = 0.7                                    % Specific Element Substitution

c = 7×7

0.6982 0.2813 0.7838 0.1135 0.2605 0.6285 0.4805 0.6335 0.1326 0.5351 0.9037 0.7807 0.5998 0.2855 0.8854 0.6318 0.6203 0.1800 0.7000 0.8871 0.0876 0.9228 0.0353 0.6748 0.8209 0.0847 0.5314 0.4022 0.7950 0.0737 0.1782 0.3322 0.5021 0.1417 0.1283 0.4916 0.2146 0.7357 0.0710 0.6016 0.2754 0.6260 0.9563 0.9825 0.0833 0.0659 0.8694 0.6343 0.6513

ct = c.';                                       % Transpose
[val,idx] = min(abs(ct(:)-0.7))                 % Return Linear Index

val = 0

idx = 19

[ccc,crr] = ind2sub(size(c),idx)

ccc = 5

crr = 3

Check = c(crr,ccc)

Check = 0.7000

.