Is it possible to identify variables in the workspace that contain a string and save the identified variable with another name?

Is it possible to identify variables in the MATLAB workspace that contain a certain string and save that variable with a new name?

For example, search for variables containing "Position" then save the found variable with a new name? I'm working with data that is imported into the workspace where the exact variable name often changes but always contains a common string.

[Stephen23]

"Is it possible to identify variables in the MATLAB workspace that contain a certain string and save that variable with a new name?"

It is possible, if you really want to force yourself into writing slow, complex, inefficient, insecure, buggy code that is hard to debug:

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

"I'm working with data that is imported into the workspace where the exact variable name often changes but always contains a common string."

So far you have not told us the most important information: how are you importing that data into the workspace? The place where you import that data would be best place to fix this very badly designed data, not later once it is already in the workspace.

Answer 1

[Stephen23]

Assuming that you are LOADing some MAT files, then the best approach is to avoid your situation entirely, for example by LOADing into an output variable:

S = load(...)

If each MAT file contains exactly one variable and you do not (easily) know its name, then you can do this:

C = struct2cell(load(..));
D = C{1};

Because you did not give any concrete information this is general advice. If you actually showed us the code you use to import into the workspace (and even better uploaded some sample data files) then we could actually write some working code very quickly.

[Jack Smith]

Hi Stephen,

The data is being loaded into the workspace from a tdms file (file format specific to National Instrruments hardware) using a TDMS read function from the file exchange, see link below.

https://uk.mathworks.com/matlabcentral/fileexchange/30023-tdms-reader

The code to load the file data into the workplace is shown below.

Struct1 = TDMS_getStruct(filename.tdms);

I can't share the data files as they are proprietary but the fomat of the data in structure "Struct1" is:

Struct1.A.variableName

where "variableName" is the variable that can change name between data files.

You're right, ideally this should be controlled in the file itself but I'm trying to see if there's a way to correct for mistakes made in the creation of the TDMS files in MATLAB.

[Stephen23]

"where "variableName" is the variable that can change name between data files."

As far as I can tell from a brief reading of TDMS Reader documentation, the function TDMS_GETSTRUCT actually returns a structure. So what you have are actually called fields (they are not called variables):

https://www.mathworks.com/help/matlab/structures.html

You can easily access the fields of a structure dynamically using e.g. FIELDNAMES() to get their names and then use dynamic field names to access their content:

https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

Field names are just text, so of course you can use any text tools to match/identify the particular fields that you want (e.g. using STARTSWITH, CONTAINS, etc).

So in the end, you might have something like this (untested of course):

F = fieldnames(Struct1.A);
X = <some logic to identify one field name in F>
D = Struct1.A.(F{X})

It also depends on the sizes of those structures, how many fields you need to access, etc.

[Jack Smith]

Hi Stephen,

Sorry, you're right that the user function returns fields and not variables. That method worked for me, I just replaced the X variable in your code with a contains filter to find the relevant fields.

X = contains(F,'string')

Thanks for your help!