diff not working on a vector of values

Question

Jason 2024-4-24

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2111291-diff-not-working-on-a-vector-of-values

评论： Jason 2024-4-24

采纳的回答： Cris LaPierre

在 MATLAB Online 中打开

Is there a reason why I cant calculate the difference between each of these values (x1)

This is the code Im using

         [x1,y1]=SpotFind_NXC(app,ax2);   %my function to locate x,y coordinates of spots in an image    
         x1
         class(x1)
         xdiff=abs(diff(x1))

and the command window:

x1 =
         98.00
         97.68
         97.75
         98.32
        221.00
        220.99
        221.32
        221.32
        344.00
        343.99
        344.33
        344.25
ans =
    'double'
Unrecognized function or variable 'diff'.

2nd Question, once it works, how can I group these into "similar values". so ideally I would want the median (or mean) of the 1st group (98.00, 97.68. 97.75, 98.32), and then the median of the 2s group around 221 and the 3rd group around 344.

Thanks

Jason

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Answer 1

Cris LaPierre 2024-4-24

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2111291-diff-not-working-on-a-vector-of-values#answer_1447171

在 MATLAB Online 中打开

There is nothing about the code you have shared that would prohibit you from using diff. For some reason, it is not on your MATLAB path. You may need to reset your path using restoredefaultpath

x1 = [98.00 97.68 97.75 98.32 221.00 220.99 221.32 221.32 344.00 343.99 344.33 344.25]';
xdiff=abs(diff(x1))
xdiff = 11x1
    0.3200
    0.0700
    0.5700
  122.6800
    0.0100
    0.3300
         0
  122.6800
    0.0100
    0.3400
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Not sure what typical values will be. You could use discretize or histcounts to bin your data. Here's one approach assuming your data is sorted.

% use xdiff to determine 
nbins = sum(xdiff>mean(xdiff))+1
nbins = 3
[N,edges,bin] = histcounts(x1,nbins)
N = 1x3
     4     4     4
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edges = 1x4
    80   170   260   350
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bin = 12x1
     1
     1
     1
     1
     2
     2
     2
     2
     3
     3
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splitapply(@mean,x1,bin)
ans = 3x1
   97.9375
  221.1575
  344.1425
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Jason 2024-4-24

Thankyou for the answer.

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Answer 2

Matt J 2024-4-24

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2111291-diff-not-working-on-a-vector-of-values#answer_1447176

在 MATLAB Online 中打开

x=[         98.00
         97.68
         97.75
         98.32
        221.00
        220.99
        221.32
        221.32
        344.00
        343.99
        344.33
        344.25];
G=findgroups(round(x,-1));
Medians=splitapply(@median,x,G)
Medians = 3x1
   97.8750
  221.1600
  344.1250
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