finding elements in array
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I have an array
vk = [0 0.025 0.05 0.075 0.1 0.125 0.15 0.175].
I am writing this line
op= vk(vk>= 0.05 & vk<= 0.175)
The result which I am getting is
op =
0.0750 0.1000 0.1250 0.1500 0.1750
which is wrong, I should get
0.05 0.0750 0.1000 0.1250 0.1500 0.1750
does anyone know what I am doing wrong?
Also how I can get the indices number of the array vk and of op?
6 个评论
Meg Noah
2020-1-10
It worked for me:
vk = [0 0.025 0.05 0.075 0.1 0.125 0.15 0.175];
op = vk(vk>= 0.05 & vk<= 0.175)
>> vk = [0 0.025 0.05 0.075 0.1 0.125 0.15 0.175];
op= vk(vk>= 0.05 & vk<= 0.175)
op =
Columns 1 through 4
0.05 0.075 0.1 0.125
Columns 5 through 6
0.15 0.175
Chris Dan
2020-1-11
no, its not working on this
Can you tell why?
Chris Dan
2020-1-11
Possibly you have issues with floating point error. Print the exact number values:
and you might find that the values are not what you think they are. See also:
This is worth reading as well:
采纳的回答
Meg Noah
2020-1-10
To get the indices to the vk array
vk = [0 0.025 0.05 0.075 0.1 0.125 0.15 0.175];
[idx] = find(vk>= 0.05 & vk<= 0.175);
op = vk(idx)
4 个评论
Stephen23
2020-1-11
find is not required, logical indexing is simpler and more efficient:
idx = vk>=0.05 & vk<=0.175;
op = vk(idx)
The OP specifically asks: Also how I can get the indices number of the array vk and of op? And that is why I have a 'find' command.
When I run this code to find the indices of the vk meeting that condition, this is what is displayed:
>> idx = find(vk>=0.05 & vk<=0.175)
idx =
3 4 5 6 7 8
Remember: matlab arrays begin indexing at position 1. There is no 0th element.
>> vk(0)
Array indices must be positive integers or logical values.
The value of element 1 is 0. Since it does not meet the condition, the index 1 is not returned on the list of indices that meet the condition.
The value of element 2 is 0.025. Since it does not meet the condition, the index 2 is not returned on the list of indices that meet the condition.
The value of element 3 is 0.025. It is the first value that meets the condition, and index 3 is the first value returned on the list of indices that meet that condition.
If your problem is floating point, then maybe try recasting it. Is it being set to a double precision array initially?
vk = double(vk);
Chris Dan
2020-1-12
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