Finding how mych values contain a specific number in a matrix

1 view (last 30 days)
I built the next matrix:
A=rand(100, 100)
I need to find how much values contain '3' in the first four digits. I would like to know how to do that.

Accepted Answer

Walter Roberson
Walter Roberson on 20 Apr 2018
 nnz(cellfun(@(S) ismember('3',S), sprintfc('%4d',floor(A*10000)))) 
  2 Comments
Walter Roberson
Walter Roberson on 20 Apr 2018
The '%4d' could be just '%d' here.
But if you were searching for 0's then you should use '%04d'
Walter Roberson
Walter Roberson on 20 Apr 2018
 B14 = floor(A*10000);
 D4 = mod(B14, 10);
 B13 = (B14-D4)/10;
 D3 = mod(B13, 10);
 B12 = (B13-D3)/10;
 D2 = mod(B12, 10);
 D1 = (B12-D2)/10;
 nnz( any([D1(:), D2(:), D3(:), D4(:)] == 3, 2) )

Sign in to comment.

More Answers (1)

David Fletcher
David Fletcher on 20 Apr 2018
Edited: David Fletcher on 20 Apr 2018

Whilst I can admire the brevity of Walter's code, I might be inclined to use a more 'conventional' alternative

A=rand(100, 100);
extract=A;
count=0;
for iter=1:4
    %Prepare integer value for examination
    extract=extract*10;
    %remove fractional part
    intVals=floor(extract);
    %running total of '3's in each column
    count=count+sum(intVals==3);
    %subtract integer portion ready for next loop
    extract=extract-intVals;
    %Remove numbers where 3 has been found
    extract(intVals==3)=0;
end
total=sum(count); 

Categories

Find more on Loops and Conditional Statements in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!