Error using plot Vectors must be the same length.

Hi I am pretty new to Matlab and I am trying to plot Acceleration and driving style against time however the time vector is not the same size. I'm not sure how I fix this.

figure(3);
plot(t_sec,Acceleration,'r');
hold on
plot(t_sec,ds_mapping,'c');

Acceleration 1x620

ds_mapping 1x620

t_sec 621x1

Please could you advise?

Thanks.

[infinity]

Hello,

The acceleration is second drivative of a position with respect to time. If you have vector of time like t = [1 2 3 ... 10] then the acceleration vector has 9 elements with respect to time of 1, ..., 9. So, for you case, you should plot the acceleration only from t_sec(1:end-1) like this

figure(3);
plot(t_sec(1:end-1),Acceleration,'r');

I don't know for the case of ds_mapping. You can think in the same maner as acceleration to plot for correct range of time.

[Guillaume]

Well, you need to find out why the two are not the same length when they should be. It's not something we can answer, and what you should do will depend entirely on what that answer is.

Perhaps, as infinity says, you've calculated the acceleration by taking the diff of the velocity which would explain why it has one element less (in which case maybe you should have used gradient instead of diff). That doesn't explain ds_mapping.

Or perhaps the explanation is something else entirely. Maybe you've loaded the wrong time vector.

[KALYAN ACHARJYA]

Please share complete code.

Answer 1

[Sourav Bairagya]

In your code, “Acceleration” and “ds_mapping”are row vectors whether “t_sec” is a column vector.

Hence, you should first convert “t_sec” into a row vector like “Acceleration”and “ds_mapping”.

Now, as your Y-axis data i.e. “Acceleration” and “ds_mapping” have 620 elements only, hence you should consider only the first 620 elements of your X-axis data i.e. “t_sec”.

A demo code is attached here to illustrate the whole plotting procedure mentioned above:

Acceleration=rand(1,620);                 % A Demo Acceleration row vector
ds_mapping=rand(1,620);                   % A Demo ds_mapping row vector
t_sec=rand(621,1);                        % A Demo t_sec column vector
 
t_sec=t_sec';                             % converting t_sec into a row_vector
 
plot(t_sec(1:end-1),Acceleration);        % Considering only 620 elements of t_sec and plotting
hold on;                                 
plot(t_sec(1:end-1), ds_mapping);
hold off;