Matrix Calculations

Matrix Threshold Count

Masked Sum

Whole-matrix comparisons produce a logical mask that can drive both count and masked sum.

Program

Play the program to change the threshold and see the selected matrix values change.

matrix_threshold_count.f90 
program matrix_threshold_count_demo
    implicit none
    integer :: values(2, 3)
    integer :: threshold
    integer :: high_count
    integer :: high_total

    values = reshape([2, 5, 8, 3, 6, 9], [2, 3])
    threshold = 
    high_count = count(values > threshold)
    high_total = sum(values, mask=values > threshold)
    print '(I0, 1X, I0)', high_count, high_total
end program matrix_threshold_count_demo

program matrix_threshold_count_demo
    implicit none
    integer :: values(2, 3)
    integer :: threshold
    integer :: high_count
    integer :: high_total

    values = reshape([2, 5, 8, 3, 6, 9], [2, 3])
    threshold = 
    high_count = count(values > threshold)
    high_total = sum(values, mask=values > threshold)
    print '(I0, 1X, I0)', high_count, high_total
end program matrix_threshold_count_demo

program matrix_threshold_count_demo
    implicit none
    integer :: values(2, 3)
    integer :: threshold
    integer :: high_count
    integer :: high_total

    values = reshape([2, 5, 8, 3, 6, 9], [2, 3])
    threshold = 
    high_count = count(values > threshold)
    high_total = sum(values, mask=values > threshold)
    print '(I0, 1X, I0)', high_count, high_total
end program matrix_threshold_count_demo
logical mask `values > threshold` compares every matrix element.
count `count(mask)` counts the `.true.` positions in the mask.
masked sum `sum(values, mask=mask)` adds only selected elements.