# How to obtain samples within angular windows?

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OH 2017 年 1 月 17 日
コメント済み: OH 2017 年 1 月 21 日
Hi, Let us say I have a projectile moving around in a square environment and I want to sample all positions where the projectile has travelled within a 20 degrees angular window, as seen from a fixed point in the environment. Can anyone help me figure out how to do this? In the attached picture, the spiral is a made up path of the projectile and the red dot is the fixed point from which I want to make the angular window.
Thanks
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OH 2017 年 1 月 18 日
Ok, so if I construct vectors with 20 degrees separation emanating from the fixed point (as in the picture below), can I then somehow get all the non-NaN elements (i.e where the projectile has been) in the area between two vectors?

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### 回答 (1 件)

Jyotish Robin 2017 年 1 月 20 日
Hi,
Since you are asking for a way in which you can get the non- NaN elements, I suppose you are having a matrix which corresponds to the image. Let me know if that is not the case.
Now, I would suggest you to make use of the function "isnan". isnan(A) returns an array with the same size as A containing logical 1 (true) where the elements of A are NaNs and logical 0 (false) where they are not.
So if it's just a 1D vector ( say y), you can simply do something like this:
>>y1 = y(~isnan(y));
Hope it helps!!
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OH 2017 年 1 月 21 日
I would say so.
If one also wants a vector with the sector identity for each
position sample, one may add the following to the example above:
sectorIdentity = (1:n) * sectorgrouping;
Thanks

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