finding the indices of the first (by index) negative number in the bottom row of a matrix

I have T = [ 1 2 1 0 0 0 120 ; 1 1 0 1 0 0 70 ; 2 1 0 0 1 0 100 ; -5 -4 0 0 0 1 0 ]

I am interested in finding the indices of the first (by index) negative number in the bottom row of any matrix T. Here, I want the index 4 1, in some form, back.

thanks!!!!

Answer 1

[Matt Fig]

An alternative,

R = size(T,1);  
LOC = [R find(T(R,:)<0,1,'first')]

[Walter Roberson]

Matt, what happens when you try that on

T = zeros(7,4);

[Matt Fig]

In that case, length(LOC)==1.

I assume brittany would have to check the results either way. With your method a call to ISEMPTY will check - either way a check should be made.

[Paulo Silva]

I think you dont need to use the argument 'first', here's a compact form:

LOC=[size(T,1) find(T(end,:)<0,1)]

[Paulo Silva]

+1 vote just because I ended up with a similar solution, Walter solution is also very good!

[Matt Fig]

Good point Paulo! I forgot about that line in the help:

I = FIND(X,K,'first') is the same as I = FIND(X,K)

Answer 2

[Walter Roberson]

[r,c] = find(T(end,:) < 0,1);
if ~isempty(r); r(:) = size(T,1); end

Answer 3

[brittany adam]

thanks thanks!! you're awesome.

[Jan]

Does this mean, that you accept one of the answers? Then please click on the corresponding button, such that others can see, that the question is solved.