Please help create a transition matrix

Question

llrb 2014-5-20

0
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https://ww2.mathworks.cn/matlabcentral/answers/130391-please-help-create-a-transition-matrix

评论： shahab anjum 2020-3-9

Hi,

I hope anyone could help me, I'm kinda new to Matlab.

I have a variable 'velocity' with the value ranging from 0-48 km/hr. I have about 2250 of these data. I would like to create a frequency matrix of the speed transition follows another speed.

Velocity :

1.28

0.57

0.75

2.88

8.05

13.7

...

I would like to make a frequency matrix with this criteria:

Explanation: cell [2,2] --> velocity < 2 is followed by velocity < 2 one time.

I really appreciate any help you give. Thank you for your time.

Best,

Ella

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Answer 1

Sven 2014-5-20

1
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Hi Ella,

The code below should do what you're looking for. I displayed the result as an image but you can just look at the final contents of freqMat

velocity = [1.28 0.57 0.75 2.88 8.05 13.7]
binEdges = 0:2:20; % 0 to 2 is the first bin, 2 to 4 is second bin, etc
[~,velBinNos] = histc(velocity,binEdges); % Histc just asks which bin each velocity belongs to
binTicks = binEdges(1:end-1); % Don't need the last bin edge
freqMat = zeros(length(binTicks));
fromBinNos = velBinNos(1:end-1);
nextBinNos = velBinNos(2:end);
for i = 1:length(fromBinNos)
    freqMat(fromBinNos(i),nextBinNos(i)) = freqMat(fromBinNos(i),nextBinNos(i)) + 1;
end
figure, imagesc(binTicks,binTicks,freqMat)
xlabel 'Next velocity bin'
ylabel 'First velocity bin'
colorbar