finding if a variable exists

I am running an if loop that creates a variable x. at a later stage if x exists I want to use to build other variables. is there any function that tells me for example if x exists x2=x*2; end

Answer 1

[Walter Roberson]

if exist('x','var'); x2 = x*2; end

However, it is seldom a good idea to create variables on the fly. Please read this FAQ