Cant plot with "if/else"

Hey I'm trying to plot this

x = To:It:Tf;
if x <= 411;
    a = 2.03 + (0.0390*x);
else x > 411;
    a = 12 + (.00273*x);
end
b = 12.62+(0.001492*x)-(76200./(x.^2));
c = (C1/100)*a + (C2/100)*b;
plot(x,a,'-',x,b,'--',x,c,'.');

But when I try to plot it, it only takes value of the second formula for a, anyway I can make the if/else condition work? Thanks!

[Purushottama Rao]

What is the value of Tf?

[Daniel]

Oh sorry To is 273, It is 5 and Tf is 498, thanks

Answer 1

[Walter Roberson]

x = To:It:Tf;
smallx = x <= 411;
a(smallx) = 2.03 + 0.0390*x(smallx);
a(~smallx) = 12 + 0.00273*x(smallx);

[Daniel]

Thanks a lot! This really fixed it!