How to calculate the coefficient of variation in Matlab

I have 90000 time data and 90000 speed data, and the time are equally averaged. I need to calculate the coefficient of variation for every 30 sec and plot it.

Here is my code, and I got 3000*3000 for the coefficient of variation. So I cannot plot it. Does anyone know how to fix it?

a=time;
b=speed;
n=30;
time_aver=reshape(a,n,[]);
speed_aver=mean(reshape(b,n,[]));
%
time_std=reshape(a,n,[]);
speed_std=std(reshape(b,n,[]));
%
speed_CV=speed_std\speed_aver;
plot(time_aver,speed_aver,'LineWidth',2);
hold on
plot(time_std,speed_std,'LineWidth',2);

Answer 1

[dpb]

N=30;
mn=mean(reshape([time(:),speed(:)],N,[]));  
sd=std(reshape([time(:),speed(:)],N,[]));
cv=reshape(sd./mn,[],N);

returns CV of time, speed as columns in cv.

[Xuefei Sun]

Hi, Thanks for your answer. But I need to plot the average speed that is maintained in that 30 sec. So the time shouldn't be averaged And how to plot the coefficient of variation now?

[Xuefei Sun]

I got what you mean. What I need is add a dot behind the molecular. Now I can get the answer. Thank you!

[Katharina Hofer]

Shouldn't it be std divided by the mean, not mean divided by the std?

[dpb]

Indeed. Good catch, @Katharina Hofer