why is my program not working ?

x=-10:0.01:10
if x<-1
    y=2*x+1
end
if x>=-1
    y=2^x+1
end
plot(x,y)

??? Undefined function or variable 'y'.

Error in ==> Untitled at 8 plot(x,y)

Answer 1

[Adam]

x is a vector so x <-1 is also going to be a vector of logicals. In your case neither of your if statements returns true so y is undefined. You need something vectorised like the following (or a for loop if you want to be deliberately inefficient!):

x=-10:0.01:10;
y = zeros( size( x ) );

y( x < -1 ) = 2 * x( x < -1 ) + 1;
y( x>= -1 ) = 2.^x( x >= -1 ) + 1;

In your code x<-1 would only return true if every element in the vector x satisfied that condition, which is obviously not the case.

Answer 2

[Purushottama Rao]

I think you are looking for something like

x=-10:0.01:10;
y(x<-1)=2*x(x<-1)+1;
y(x>=1)=2.^x(x>=1)+1;
plot(x,y)