Difficulties in axes scaling on matrices: 500 values should be 200 Hz - how to handle?

2012 9 10
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Hello community,
As described I have difficulties in scaling axes on 3d (or 2d) plots.
For example I have a 100x500 matrix = A
Due to the resolution in data aquisition I have 100 Values on the time axe y and 500 values on the frequency axe x.
I want an easy way in coding that those 500 values describing 200 Hz, and that those 100 Values describing 6 hours.
Until now I always changed the width of the matrix with a factor, so that I only have 200 values.
if true
% maxfr1=zeros(109,1);
maxfr2=zeros(109,1);
maxfr3=zeros(109,1);
maxfr4=zeros(109,1);
for i1= 1:109
maxfr1(i1,1)=maxidx_smooth1(i1,1)*0.39;
maxfr2(i1,1)=maxidx_smooth2(i1,1)*0.39;
maxfr3(i1,1)=maxidx_smooth3(i1,1)*0.39;
maxfr4(i1,1)=maxidx_smooth4(i1,1)*0.39;
end
end
When I plot a 2d or a 3d graph its shown correctly then. But this is very uncomfortable and erases my higher resolution in data aquisition. Until now I have not found a way to do it easily interactive (change ticks only adds or deletes values but is not changing the whole scale)...
I certainly need help :)
Thank you

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Jan
Jan 2012-9-10
编辑：Jan 2012-9-10

1 个投票

At first you could cleanup the posted code - you do not nee a loop:
maxfr1 = maxidx_smooth1 * 0.39;
maxfr2 = maxidx_smooth2 * 0.39;
maxfr3 = maxidx_smooth3 * 0.39;
maxfr4 = maxidx_smooth4 * 0.39;
It would be even easier, if you store the vectors in one matrix.
But I assume, I do not understand the actual problem.
[EDITED]
It would be clearer, if you post Matlab code, which reproduces your problem. I assume you need to specify the values of the X-direction:
y = rand(50, 10); % Smaller for simplicity
figure
plot(y); % Your problem, x-values are the indices
figure
x = linspace(0, 200, 50);
plot(x, y); % Scaled x-values

更多回答（2 个）

Florian
Florian 2012-9-10

0 个投票

OK. I try to describe it easier.
I need a 2d plot of a matrix. The matrix has the dimensions 100x500.
I recorded the data in the matrix with 3 values per second for a higher resolution.
If I want to plot the matrix now - the x-axis goes from 0 to 500. Those 500 values representate lets say 200 Hz. So in the plot there shouldn´t be shown the number of values i have - "500" BUT INSTEAD the 200 Hz but on the same location where now "500" is...
If I do change "X-Limits" which is now from 0 to 500 into 0 to 200 it simply just cuts off the rest of the graph. But I want the whole graph displayed just with the x-axis scale 0 to 200.
I hope this was understandable - picture didn´t work.
Thanks

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Jan
Jan 2012-9-10
编辑：Jan 2012-9-10
What does "picture didn't work" mean?
Instead of "if I want to plot..." post the corresponding code, because the actual problem is hidden in it.
Florian
Florian 2012-9-11
Hello again,
sorry for confusion - in my head the problem description sounds logical ;)...
if true
% scale problems with plot
% %%create matrix
A = rand(109,512);
for i= 1:10
A(:,40+i)=30;
end
% %%create plot
figure1 = figure(1);
plot1 = surf(A);
%plot1 shows now a 3d plot with 512 values in x-direction, 109 in
%y-direction and 30 values in z-direction. the values of the x-direction
%are showing a frequency range from 20 to 200 Hz. This means i have to
%"rename" the x-axis scales that it is shown correctly in the figure.
%Otherwise someone who dont knows what i have done, thinks we have a
%frequency range from 0 to 500 Hz. end
Jan
Jan 2012-9-11
There is no reason for apologies, because you are the only one who suffers from missing answers.
Have you seen my new suggestion after the [EDITED] tag?
Florian
Florian 2012-9-11
I have tried the linspace function and its pretty good. Sounds like that what I needed. Are there any ways to do this interactive - when the plot is already created?
Thanks
Jan
Jan 2012-9-11
Yes.
Set(AxesHandle, 'XData', linspace(0, 200, 50))
The AxesHandle can ge found e.g. by clicking on the axes and using gca afterwards.
Florian
Florian 2012-9-11
编辑：Florian 2012-9-12
Ok works great now but just for 2d graphs....!!! Thank you very much for your effort !!!

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Florian
Florian 2012-9-12
编辑：Florian 2012-9-12

0 个投票

ok as i told you the linspace function works with 2d plots.
but i have another problem with a 3d plot: Please try this
GG2 =rand(109,512);
figure43 = figure(43);
surf(GG2)
figure44 = figure(44);
x = linspace (20,200,2);
surf(x,GG2(:,1),GG2);
I do want the same graph than in figure43 but the x-axis range should go from 20 to 200 and not from 0 to 600.
The figure44 shows nothing...
Is this possible somehow?
Regards,

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