Evalin Loop Workspace fints

Hello,

I am stuck on how to code in order to able to work with workspace variables.

I am struggling to include and indexing the evalin function in a loop. I used the who but its not really working.

I have 5 tables with different names in the workspace, they are of type fints.

I want to create a dataset which will merge/concatenate, one column of each five tables into one global array.

The fints(time series object) table have 5 columns, I want the close(3rd) column. To access it, u need to type TableName.Close.

I know this can be done with cell arrays, but here i am working with fints.

Thank you very much

Davin

[Davin]

I have tried to following but not really working,

    Global = []
    a = who
    for i = 1:length(a)
    Data = a(i).Close
    Global = [Global; Data(:,3)]
    end

This one too :

Global = []
    a = who
    for i = 1:length(a)
    Data = evalin('base', [a{i}.Close])
    Global = [Global; Data(:,2)]
    end

I think there are 2 issues, iterating on who, is not great, because it creates an intermediary array, so on second execution, it will count intermediary tables. Also the fints table.

Any suggestions?

Answer 1

[Geoff Hayes]

Davin - have you tried stepping through the code to see what is happening? Let's suppose that you have a function called myFunc, and you have the five (fints) tables in the workspace. In the Command Window you type

 myFunc

Now suppose the definition for this function uses your second code example

 function myFunc

 Global = []
 a = who
 for i = 1:length(a)
    Data = evalin('base', [a{i}.Close])
    Global = [Global; Data(:,2)]
 end

The first line of code declares an empty array named Global. This should be renamed so as not to be confused with the built-in MATLAB global "qualifier" for global variables. Perhaps name it given the data that is being used to populate it: allCloseData. The next line calls the who function which, since we are evaluating it from a function, will return only those variables that have been declared in this function. I think that you want to grab the variables in the base workspace. So try

 allBaseVars = evalin('base','who');

Now, you iterate over each one and grab the last (close) column. You mentioned that you are concerned with accessing variables that aren't of type fints - so just add a check on the class type

 for k=1:length(allBaseVars)

    classType = evalin('base',['class(' allBaseVars{k} ')']);
    if strcmpi(classType,'fints')
       % do stuff
    end
 end

I don't have the Financial Toolbox so I'm guessing that the class type of a Financial Time Series object is fints. You can verify this easily enough by just type class(myFintsTable) in the Command Window and seeing what is returned.

Now we can "do stuff" if the object is of type fints. The code will be similar to what you have shown, but the expression (the second input to evalin) must be a string and not the statement hat you have shown

 data = evalin('base',[allBaseVars{k} '.Close']);
 allCloseData = [allCloseData ; data];

So your function now becomes

 function myFunc

 allCloseData = [];
 allBaseVars  = evalin('base','who');

 for k=1:length(allBaseVars)

    classType = evalin('base',['class(' allBaseVars{k} ')']);
    if strcmpi(classType,'fints')
       data = evalin('base',[allBaseVars{k} '.Close']);
       allCloseData = [allCloseData ; data];    
    end
 end

If you want to assign the allCloseData to the base workspace, then just add the following line of code to your function

 assignin('base', 'allCloseData', allCloseData);

[Davin]

Thanks once more Geoff. In the mean time, I succeeded to resolve it with something a bit like you but with some more line of codes and without the strcmpi. I used a fts2mat to put it in a double array and then a horzcat to make the global array. Your version is much more optimised.. Thanks again.

[Davin]

function myFunc
 allCloseData = [];
 allBaseVars  = evalin('base','who');
 for k=1:length(allBaseVars)
    classType = evalin('base',['class(' allBaseVars{k} ')']);
    if strcmpi(classType,'fints')
       data = evalin('base',[allBaseVars{k} '.Close']);
       allCloseData = [allCloseData ; fts2mat(data)];    
    end
 end

Apparently, the concatenate does not work with fints, it requires a double, so i added a fts2mat to transform the data array. Now it works, I removed purposedly the date in the array.

May be there is a better way without passing by fts2mat...

cheers