Function sort and smooth in matlab

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Shalini 2012-4-10

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1) Consider the function sort:

You can call it with as below;

B = sort(A)
B = sort(A,dim)

If A is a vector, do I need the argument dim?

2)Now, consider the function smooth;

suppose I suply bot the independent variable x and dependent variable y as below;

yy = smooth(x,y,...)

Is it mandatory that I should be sorting all values of x in acending order before I plot?I mean does smooth carry out smoothing with x arrranged in ascending order?

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回答（1 个）

Walter Roberson 2012-4-10

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1) If you are sorting a vector, you need to supply dim if you care about which direction the vector is sorted on.

In particular, it is possible that you expect your A to be a full array but there are conditions under which you might possibly get out a vector (e.g., a single row when you expect many rows.) If you do not specify the direction the sort could accidentally be a direction you did not expect.

2) http://www.mathworks.com/help/toolbox/curvefit/smooth.html

yy = smooth(x,y,...) additionally specifies x data. If x is not provided, methods that require x data assume x = 1:length(y). You should specify x data when it is not uniformly spaced or sorted. If x is not uniform and you do not specify method, lowess is used. If the smoothing method requires x to be sorted, the sorting occurs automatically.

Note that final sentence.