I want to get the difference between the present number and the previous number for 1000 set of data from the plot.

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Surabhi A S 2022-8-22

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https://ww2.mathworks.cn/matlabcentral/answers/1783510-i-want-to-get-the-difference-between-the-present-number-and-the-previous-number-for-1000-set-of-data

评论： Surabhi A S 2022-8-23

采纳的回答： Cris LaPierre

For example,

I have considered 10 random values from the set of 1000 values

X-axis values are as given a = [ -9.658 -9.321 -8.979 -8.742 -8.247 -7.291 -6.738 -7.439 -8.733 -8.596 ]

Y-axis values are as given b = [134 135 136 137 138 139 140 141 142 143 ]

I want to consider each set of values and find the difference between the number and its previous number for example a2-a1,a3-a2,a4-a3.... till a1000-a999. Depending upon these values if its increasing(difference is positive) or decreasing(difference is negative) or constant(difference is zero) I have to find out the threshold value of the given set. Please help me with the code.

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Cris LaPierre 2022-8-22

在 MATLAB Online 中打开

Do you mean a2-a1,a3-a2,a4-a3,...., a1000-a999?

If so, use the diff function.

a = [ -9.658  -9.321  -8.979  -8.742  -8.247  -7.291  -6.738  -7.439  -8.733  -8.596  ];
c=diff(a)
c = 1×9
    0.3370    0.3420    0.2370    0.4950    0.9560    0.5530   -0.7010   -1.2940    0.1370

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Cris LaPierre 2022-8-22

I don't understand why you need a while loop to do that. Diff uses exactly the formula you wrote.

Y = diff(X) calculates differences between adjacent elements of X along the first array dimension whose size does not equal 1:

If X is a vector of length m, then Y = diff(X) returns a vector of length m-1. The elements of Y are the differences between adjacent elements of X.

Y = [X(2)-X(1) X(3)-X(2) ... X(m)-X(m-1)]

Surabhi A S 2022-8-22

Thank you

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the cyclist 2022-8-22

在 MATLAB Online 中打开

a = [2 3 5 7 11];
a - a' % All possible differences between pairs of elements of a
ans = 5×5
     0     1     3     5     9
    -1     0     2     4     8
    -3    -2     0     2     6
    -5    -4    -2     0     4
    -9    -8    -6    -4     0