Find the row number of element that meets the condition

I am trying to use find command to locate row number of the first elements which meets the condition.

All I am able to do right now is to find elements themselves which meet the condition I gave.

How can find the row number (in matrix A) which meets the condition first. I wanted to use this row number further find relevant element value from another array.

for example:

A=[450;470;490;510;530;550;570];

B=[10;20;30;40;50;60;70];

so if I use condition A>500 , answer would be 40.

I tried using following command

C=A(A>500)

but it is giving me all the values of element and not row number, which further will be used to find element from B array having same row number.

Answer 1

[madhan ravi]

index=find(A>500,1,'first')
B(index)

[Prasad Raut]

Thanks :)