How to get 'type' of a variable in matlab?

Hi, We declare many types of variables in matlab such as double, string, symbolic etc. How to get type of a variable?

Answer 1

[Sean de Wolski]

To get the data type, or class, of a variable, use the “class” function.

x = 100;
class(x)

To determine if a variable has a specified data type, use the “isa” function.

tf = isa(x,'double')

For a list of functions that determine if variables have specific attributes, see “is*”.

You also can use the “validateattributes” function, which can validate many classes at once easily.

Answer 2

[Azzi Abdelmalek]

class(your_variable)

[Robert Bruner]

"Error: the class function must be called from a class constructor"

how can I do this from the command-line in MATLAB?

[Bill Tubbs]

I have the same problem.

>> class(theFiles)

ans =

'struct'

>> class(theFiles.name)

Error using class

The CLASS function must be called from a class constructor.

[Steven Lord]

I'm guessing theFiles is a non-scalar struct array, which would mean that theFiles.name is a comma-separated list. This makes MATLAB think you're using a different syntax for the class function, one associated with the older style of classes. See the "Obsolete Class Definition Syntax" section on the class documentation page.

You could try:

class(theFiles(1).name)
class(theFiles(2).name)
% etc

[Mahalakshmi Sivakumar]

how to use this class inside .m script it throws a char but i want parameter

[Steven Lord]

I don't understand your question. Could you explain what you mean by "it throws a char" and "i want parameter" in a little more detail?

[ANTONIO RUBIA]

I think I undesrstod the question because I have a similar problem. Please check this example:

clear all
a = randn(5,1);
b = randn(5,1);

list = who;
Check=cell(2,1);
for j=1:2
    Check(j)={class(list{j})}
end

Check is supposed to retrieve programatically the classes of the variables in the workspace (namely, "double" for a nd b). However, it literally reads the class of the argument passed in, i.e., retrieves "char" in both cases. How to programatically get the class of the variables stored, for instance, in the workspace?

[Stephen23]

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

[Steven Lord]

How are you planning to use that information? There are ways to get access to this information (the whos function is one) but depending what you want to do with that information there may be better / safer alternatives.

[ANTONIO RUBIA]

Dear Steven, thank you for your constructive and useful answer. My plan is to use that information in an app environment similar to the Import Data functionality of the Econometric Modeler app. The point is to allow the user to import data from the workspace into the main app by selecting the variables listed on a table by rows, with columns showing different information (name, class, size, etc.).

The function whos you suggested does the job. In my case, something like:

info = evalin('base', 'whos')

collects all the information meant to be reported in the selection table and can be processed programatically in a function. Your suggestion should help clarify M. Sivakumar's earlier question too.

This is already a valid solution, but in case you may have better /safer alternatives, I would definitively love to know more about them.

Thanks !