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Priya
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error using plot:Vectors must be the same lengths

Asked by Priya
on 19 Aug 2014
Latest activity Commented on by Priya
on 20 Aug 2014
I get this error in the plot line.
V=20;
t_sim=0.02;
sample_distance=0.2;
ts=sample_distance/V;
step_time=1;
step_size=0.01;
collect_ts=ts*1;
t_plot=(0:collect_ts:t_sim);
figure(6);
plot(t_plot,simout(:,1));hold all;plot(x,y);grid on;
xlabel('Time (s)');ylabel('lateral position (m)');
>> size(t_plot)
ans =
1 3
>> size(simout)
ans =
21 71
Can anyone please tell the reason for this error and how to solve it.

  4 Comments

Show 1 older comment
Thank you. Could you please find my below comment and see if you can help me out.
I'm afraid I don't know anything about Simulink, but I would still suggest that if you think those two quantities should be able to be plotted against each other and if the simout variable is correct then you need to look at how you are defining t_plot.
If your min and max are absolutely correct then
t_plot = linspace( 0, t_sim, 21 )
would at least give you the right length of vector, but I can't say if that would be correct or not.
Thanks. I will check it out.

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1 Answer

Answer by Kyle
on 19 Aug 2014

I tried to reproduce your error, but the variables "simout," "x," and "y" are undefined in your included code.
Vectors must be same lengths suggests your rows and columns are not the same for t_plot and simout. It looks like t_plot has 1 row and 3 columns, while simout has 21 rows and 71 columns.

  5 Comments

simout is the output from the model to the workspace.
Since your simout is 71 columns, t_plot should be too. Are you sure you want to plot t_plot,simout on the same plot as x,y? I ask because the max for t_plot = t_sim = 0.02, while x max is 5. When plotted together you can't clearly see the t_plot,simout (see plots below). The following works as an example:
simout = 0.01*rand(1,71);
d = 0.01; x=[0,1,1,5]; y=[0,0,d,d];
t_sim=0.02;
sample_distance=0.2;
V=70; %changed
ts=t_sim/V; %changed
step_time=1;
step_size=0.01;
collect_ts=ts*1;
t_plot=(0:collect_ts:t_sim); %collect_ts (and ts) must equal t_sim/(71-1)
figure(6);
plot(t_plot,simout); grid on; hold all; plot(x,y);
xlabel('Time (s)');ylabel('lateral position (m)');
Although I didn't use the sample_distance variable at all.
This has given me some clue. Anyway thanks for your help.

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