trying to create a simple plot. Get error 'Vectors must be the same length'

I am trying to plot a function of time, and its time derivative, in a 3d plot.

This is what I typed

t = [0:0.1:4]
x = exp(-(4-sqrt(3))*t)+exp(-(4+sqrt(3))*t)
v = diff(x)./0.1
plot3(x,v,t);

and I get the error " 'Error using plot3 Vectors must be the same lengths.'"

Answer 1

[Sean de Wolski]

When you take the diff of t it subtracts each element of t from the next element leaving t one element shorter

diff(1:3)

doc diff

To plot with diff typically I zero or nan pad the input to diff or to plot.

plot(x,[v 0],t)

Answer 2

[Wayne King]

Because when you use diff(), you end up with vector with one less element, so that t and x are one element greater in length than v.

t = [0:0.1:4];
x = exp(-(4-sqrt(3))*t)+exp(-(4+sqrt(3))*t);
v = diff(x)./0.1;
plot3(x(2:end),v,t(2:end));

or do what Sean suggests.

Answer 3

[Azzi Abdelmalek]

t = [0:0.1:4]
x = exp(-(4-sqrt(3))*t)+exp(-(4+sqrt(3))*t)
v = gradient(x)./0.1
plot3(x,v,t);

%or

t = [0:0.1:4]
x = exp(-(4-sqrt(3))*t)+exp(-(4+sqrt(3))*t)
v = diff(x)./0.1
plot3(x(2:end),v,t(2:end));