Error using plot Vectors must be the same lengths.

x=0:4*pi;
y1=3.0*cos(x)-0.5*sin(x);
y2=diff(y1);
plot(x,y1,'r',x,y2,'b')

i want to plot those y1 , y2 in one graph but it said

Error using plot
Vectors must be the same lengths.

what should i do???

Answer 1

[Stephen23]

Use gradient instead of diff:

y2 = gradient(y1);

[kun hyung kim]

OMG you're a genius like a Alphago