# Error using plot Vectors must be the same length.

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Emma Windsor on 15 Aug 2019
Answered: Sourav Bairagya on 19 Aug 2019
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
Thanks.
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Guillaume on 15 Aug 2019
Edited: Guillaume on 15 Aug 2019
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 on 15 Aug 2019

Sourav Bairagya on 19 Aug 2019
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;