Sum of array items into another array
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I need to find the sum of items within each of the 360 arrays and then make another array with just the sums.
8 个评论
James Tursa
2016-6-22
You haven't given us enough information to help you. What specific items? How are your arrays stored? You need to give us a short example that shows exactly what you want to do.
Kirby Fears
2016-6-22
Are your 360 arrays floating around separately in your workspace, or are they all part of one cell array, struct, or ND+1 array?
np
2016-6-22
Kirby Fears
2016-6-22
编辑：Kirby Fears
2016-6-22
That looks like elements of a struct or columns of a table. What is the type associated with "data" in your workspace?
np
2016-6-22
Kirby Fears
2016-6-22
编辑：Kirby Fears
2016-6-22
np,
You indicated the data is in your workspace as data.speed1, data.speed2, etc.
In your workspace window, what is the data type of "data"? If it has fields speed1, speed2, etc, then "data" must be a table or struct. Please let me know which type it is so I can help.
np
2016-6-22
Kirby Fears
2016-6-22
I understand that the values inside of speed1 and speed2 are numeric, but you wrote your example as "data.speed1". So are speed1 and speed2 contained in a workspace variable called data or not?
采纳的回答
Kirby Fears
2016-6-22
Assuming data is a struct with fields speed1, speed2, etc.
sumArray = structfun(@sum,data);
更多回答（2 个）
Guillaume
2016-6-23
If your structure has fields other than the speed fields, you can loop over a hardcoded number of speed fields:
numspeed = 360;
speedsum = zeros(numspeed, 1);
for speedidx = 1:numspeed
speedsum(speedidx) = sum(data.(sprintf('speed%d', speedidx)));
end
Shameer Parmar
2016-6-23
for i=1:length(fields(data))
s(i) = sum(eval(['data.speed',num2str(i)]));
end
6 个评论
DO NOT USE EVAL. Please don't provide solutions that use eval, that's just encouraging bad programming practices, particularly when there are better solution.
s(i) = sum(data.(['speed',num2str(i)]));
Also, the proper method for obtaining the fields of a structure is fieldnames. fields is a undocumented function that may disappear or change behaviour in future versions of matlab.
In any case, Kirby's answer is much better.
Avoid using eval for trivial code like this. Here is why:
It would be much better to use the functionality that MATLAB already has to allow fieldnames to be defined via strings:
np
2016-6-23
np
2016-6-23
Guillaume
2016-6-23
1) Use fieldnames instead of fields. That won't solve the immediate problem as they both provide the same result, but fields is not supported whereas fieldnames is.
2) You get this error because your data has fields other than the 360 speed fields.
Shameer Parmar
2016-6-24
Hello np..
I guess your length of fields(data) is more that 360, that why..
If yes, you can apply one more filter like..
for i=1:length(fields(data))
if i<=360
s(i) = sum(data.(['speed',num2str(i)]));
end
end
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