MATLAB: MATLAB displays a blank graph when I plot try to plot

plotplotting

It is not empty, it has the points. Do the following change:

change the plot line to

   plot(di(ii),slope(ii),'o')

Put

xi = 0;
xf = pi; % or whatever your desired start and end values are.
f = NumIntf(xi,xf)

in a script and run that - it worked for me.

f = @(x)5*x + (x > 2)
plot(0:1e-4:3,f(0:1e-4:3))

OR:

x=0:0.0001:2;
y=5*x;
x1=2:0.0001:3;
y1=5*(x1)+1;
plot([x,x1],[y,y1]);