Create a function from a table

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alpedhuez
alpedhuez 2018-3-24
评论： Star Strider 2018-3-24
Suppose I have a matrix
A = [ 3 0.1; 1 0.2; 2 0.3];
I now want to have a function that takes an entry of the first column and gives the entry in the second column.
In other words, I want to have a matrix B where, for each element in the first column, its second column is the entry of the corresponding second column in A. For example,
B = [ 2 0.3; 2 0.3; 3 0.1; 1 0.2];
Please advise.

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采纳的回答

Star Strider
Star Strider 2018-3-24
Try this:
A = [ 1 0.1; 2 0.2; 3 0.3];
A2fcn1 = @(k) A(k,2);
SecondColumn = A2fcn1(2)
SecondColumn =
0.2000
If you want to interpolate instead, use the interp1 (link) function.

更多回答（1 个）

Walter Roberson
Walter Roberson 2018-3-24
Given any finite sets of example values, there are aleph-one (the infinity of cardinal numbers) functions that will exactly calculate the given values to within round-off error. There is no way to automatically choose between these functions as one being "better" than the other -- not unless you specify before-hand which forms of function are to be preferred.
  1 个评论
alpedhuez
alpedhuez 2018-3-24
Not that complicated. The question is how to efficiently fill in the second column of B given A and the first column of B.

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