# how to create a structure?

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gjashta on 5 Nov 2019
Commented: Walter Roberson on 6 Nov 2019
I have a data set (DATA) that contains 100 stations with daily prices and demand.
Using this code I can have 100 stations with the data that belong to each of them.
Can you help me to fix the code??
N=length(DATA(:,1))
for i=1:N
x=DATA(i,1)
station=['S', num2str(x)]
station=[station;DATA(i,:)]
end

#### 1 Comment

Stephen Cobeldick on 5 Nov 2019
Using numbered variables is a sign that you are doing something wrong.
Indexing is simple and efficient (unlike what you are trying to do).

Walter Roberson on 5 Nov 2019
You can use num2cell to split the data into cell array by column.
You can construct an array of field names in a couple of ways, including using sprintfc or string objects with the + (concatenation) operation.
Once you have both of the above you can use cell2struct to create your structure.
However we wonder why you are not just leaving the data in the numeric matrix, as that is the fastest and smallest storage?

gjashta on 5 Nov 2019
It’s a bit hard for me to understand your code but thank you very much for the time you spent Walter and your help.
Walter Roberson on 5 Nov 2019
I would suggest that you spend some time studying the documentation for accumarray(). It can take a bit of getting accustomed to, but it can be very useful.
Alternately you might want to read about findgroups(), and grpstats(), and splitapply(), which can do similar tasks in ways that are sometimes less cryptic.
(If you do use splitapply() then be sure to use @(x) mean(x,1) instead of just @mean, to account for the possibility that there might only be a single row of data for a combination.)
Walter Roberson on 6 Nov 2019
I have not done much work with linear regression.