Generate a evenly spaced array based on two arrays

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Jamee Lin 2015-4-30

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评论： Image Analyst 2015-5-1

采纳的回答： Stephen23

在 MATLAB Online 中打开

Hi,

I have one set of starting and ending points:

s_pt = [1,8,15];
e_pt = [3,12,20];

Now I would like to generate a evenly spaced array based on the corresponding starting and ending points. In this case, there would be three sets of data: (1-3, 8-12, 15-20). The answer would be like:

answer = [1,2,3,8,9,10,11,12,15,16,17,18,19,20]

Are there any functions to generate this kind of data without using for loop?

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Jamee Lin 2015-5-1

Because it takes more time and occupied more memory with for loop.

Guillaume 2015-5-1

编辑：Guillaume 2015-5-1

This is actually something I submitted as a cody problem a while back.

And this is the reverse problem I also submitted.

If you want to see all the solutions you would have to submit a valid solution (of any size) in the first place and then solve any other cody problem.

Note that the best scoring cody solution is unlikely to be the most efficient one.

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Stephen23 2015-5-1

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编辑：Stephen23 2015-5-1

在 MATLAB Online 中打开

>> s_pt = [1,8,15];
>> e_pt = [3,12,20];
>> cell2mat(arrayfun(@(s,e)s:e, s_pt, e_pt, 'UniformOutput',false))
ans =
   1     2     3     8     9    10    11    12    15    16    17    18    19    20

Although using a loop is likely to be faster...

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Jamee Lin 2015-5-1

Thanks. This works. But, yeah, in this case, for loop is faster so I'll go with a loop.

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Image Analyst 2015-5-1

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Is this homework? It sounds like homework, so I'll just give a hint for now. Use the colon operator (look it up) or, if you want a somewhat different way, use linspace(). You're going to have to learn the colon operator VERY soon if you want to do anything in MATLAB, so start now.

Hint:

8:12 is equal to an array 8,9,10,11,12. You can literally do the assignment in one single line of code.

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Jamee Lin 2015-5-1

Yes, this is what I have now. But I was thinking not to use for loop.

Image Analyst 2015-5-1

Like Stephen mentioned, and you noted in your comment to him, for loops are not always the slowest approach . You could even speed this up even more if you preallocated space for "out" with the zeros() function.

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