Why this ERROR is coming

M=1;Kp=100;
P2=M+(1/Kp);P3=P2+1i*w;
U7=exp(y*sqrt(P3)).*(1-erf(y/(2*sqrt(t))+ sqrt(P3*t)));

Error using erf (error function)

Input must be real and full.

Error in

U7=exp(y*sqrt(P3)).*(1-erf(y/(2*sqrt(t))+ sqrt(P3*t)));

[KSSV]

Undefined function or variable 'w'.

[MINATI]

oooh sorry

w=1;    t=1;
y=0:0.1:5;

[KSSV]

Undefined function or variable 'y'.

[MINATI]

Already given

y=0:0.1:5;

[KSSV]

Read about erf it accepts only real......in your case the input is complex.

[MINATI]

ok

[Walter Roberson]

There is a way you can get around the restriction. If you use the symbolic toolbox, then the erf() function for it accepts complex inputs. To use the symbolic toolbox, at least part of the expression needs to be symbolic. For example if instead of sqrt(P3*t) you used sym(sqrt(P3*t)) then that would be enough. The result of the erf would be symbolic, so you would probably want to double() it.

[Torsten]

Or maybe another alternative:

https://de.mathworks.com/matlabcentral/fileexchange/18312-error-function-of-complex-numbers