Headers in Matlab

Hello, my problem is the following one. I have data say of the following kind:

Iter X Y Z
1 30 40 50
2 50 60 70
3 30 70 80

I want to be able to store the data in different columns by invoking the headers. To explain it better, if the variable "data" contains all the information, then when I say data['Iter'] I should be able to obtain the column [1,2,3]. I have learnt this from python and I want to know if this is possible using Matlab.

Chiara

Answer 1

[Chiara Modenese]

Thanks to all but I think that only Walter got my question. I know about structures. However, my task is to save a column variable by only knowing the name of the corresponding header. In the end I should be able to write something like

iter=data('iter')

This is very useful when you import different files which share similar headers but where similar variables have different positions. I would simply like to avoid to retrieve the number of the column of each variable am interested in from each single file. If we could remember the name of the variables (like iter), then it would be a peace of cake to store what we want.

Chiara

[Walter Roberson]

You can use dynamic field names.

for K = 1 : length(headerfields)

thisname = headerfields{K};

data.(thisname) = datavalues{K};

end

You can now retrieve by data.Iter (for example) without having to know which column it occurred in.

[Chiara Modenese]

Thank you, this answered my question. To be more precise, the third line of your code should be:

data.(thisname{1})

given that headerfields is a cell array (at least is so in my case).

Chiara

[Walter Roberson]

Only if you have a cell array of cell arrays; the more usual case of a cell array of strings would use the code I showed.

[Matt Tearle]

If it's coming from textscan, it might well be as a cell array of cell arrays.

Chiara, do you have Statistics Toolbox? Because if you do, it really sounds like dataset arrays will make your life easier.

[Chiara Modenese]

Yes, sorry, I used a cell array of cell arrays as you point out.

And yes, Matt, I have that tool. I will try to use dataset instead of structures, as it seems it would simply my task a lot.

Answer 2

[Matt Tearle]

Perhaps dataset arrays are what you're looking for?

The syntax isn't exactly what you've specified, but you can refer to columns by name, similar to structures. You can read data from file (including column headers) directly with dataset.

Answer 3

[Walter Roberson]

You will not be able to do what you want with that syntax. You would be able to use data('iter'), if you went through a long exercise of programming a new data class. Or you could go for the Database Toolbox.

Answer 4

[Andrew Newell]

You can do something similar using structures:

data.Iter = [1; 2; 3];
data.X = [30; 50; 30];
data.Y = [50 60 70];
data.Z = [50 80 80];

data.Iter

ans =

     1
     2
     3