Function sort and smooth in matlab

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Shalini
Shalini 2012-4-10
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?

回答(1 个)

Walter Roberson
Walter Roberson 2012-4-10
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.
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.
  13 个评论
Shalini
Shalini 2012-4-11
@Geoff,Jan,Walter:
Please correct if I'm wrong and sorry if I'm fundamentally wrong.
We can sort with either dimension =1 or diemnsion =2.
When dimension =1 (during sort) the function 'sort', just arranges all the columns in ascending order.
When dimension =2 (during sort) the function 'sort', just arranges all rows in ascending order.
This is what (I think) is happening in the examples in this link:
http://www.mathworks.in/help/techdoc/ref/sort.html

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