How to find x?

How do I find the first value which is <1 in every column of a matrix?

[Cedric]

Do you need row indices or values? Do all columns have such an element or are there columns with all elements >= 1?

[Cedric]

Assuming that all columns have at least one element <1, here is one way:

 >> X = rand( 6, 4 ) + 0.5 ;  X(end,:) = 0.1 ;  X       % Build test case.
 X =
    1.1557    1.2431    0.7769    1.4502
    0.5357    0.8922    0.5462    0.5344
    1.3491    1.1555    0.5971    0.9387
    1.4340    0.6712    1.3235    0.8816
    1.1787    1.2060    1.1948    1.2655
    0.1000    0.1000    0.1000    0.1000

 >> firstLt1 = arrayfun( @(c)X(find(X(:,c)<1, 1), c), 1:size(X,2) )
 firstLt1 =
    0.5357    0.8922    0.7769    0.5344

If some column(s) may not have any element < 1, you can do the following instead:

 >> firstLt1 = arrayfun( @(c)X(find(X(:,c)<1, 1), c), 1:size(X,2), 'UniformOutput', false ) ;

which outputs a cell array. Columns of X with no element < 1 lead to cells that contain empty arrays.

[Image Analyst]

[Cedric]

Math puns are the first sine of madness!