MATLAB: Assign numbers to observations

namingobservation names

Hi I have a large dataset involving observations of names in a cell like below.

ABC1
AB56
AC46
AC90

I have another dataset "values" that is made up of doubles, with observations for each of the names listed above.

3x8 doubles
3x8 doubles
6x8 doubles
5x8 doubles

The datasets are specifically ordered so that the third observation in "values" has the third name. I want to give each name a number referring to its position in the original vector. E.g. AC90 is the fourth in the list so everywhere AC90 appears, the number 4 is listed.

Best Answer

If the names, values and their order should be represented, store them e.g. in a struct array:

S(1).Name = 'ABC1';
S(1).Data = <3x8 doubles>
S(2).Name = 'AB56';
S(2).Data = <3x8 doubles>

and so on. Now S(k) contains the k's data set with its name.

Cells are an alternative:

NameList = {'ABC1', 'AB56', 'AC46', 'AC90'}
DataList = {3x8 doubles, 3x8 doubles, 6x8 doubles, 5x8 doubles}

Now the name NameList[k} corresponds to the data DataList{k}. As far as I understand, you have this data format already.

Trying to create a variable, which is called 'AC90' would be a very bad idea, see Answers: Don't EVAL!.

Another idea would using the names as fieldnames:

S.ABC1 = <3x8 doubles>
S.AB56 = <3x8 doubles>
...

Then:

key = 'AB56';
S.(key)

Related Solutions

MATLAB: Concatenate arrays within a loop,

Easy, given any number of arrays in a cell array C. You could use a loop like this, although it is inefficient because the output array is not preallocated:

C = {[1,2],[3,4],...} % cell array of arrays.
A = C{1};
for k = 2:numel(C)
    A = [A;C{k}];
end

Simpler and more efficient would be to concatenate them all at once, without a loop, e.g.:

A = vertcat(C{:})

Whatever you do, do NOT try to access variable names dynamically in a loop! Read this to know why:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Using an array (e.g. a cell array) and indexing is much simpler, neater, much more efficient, less buggy, and easier to debug.

MATLAB: Is there any way to convert variables from list to arrays

Simply store the data in one structure, and then it is trivially easy (no slow, buggy eval is required):

>> S.a = [1,2,3];
>> S.b = [2,3,4];
>> C = {'a','b'};
>> S.(C{1})
ans =
   1   2   3

Simpler code through better code design: faster, neater, simpler, more efficient, easiest to debug, less complex. Why waste your time learning bad ways to write code?:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Best Answer

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MATLAB: Concatenate arrays within a loop,

MATLAB: Is there any way to convert variables from list to arrays

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