Fixes data conversion and validation

Addresses issues in data conversion from double format by correcting a conditional check for sampling frequency.

Also, this commit enhances input validation in the Struct data type checker by ensuring that the correct fieldname is retrieved, preventing potential errors when processing data structures.

Author: Nabarb

+datareader/+convert/Double.m

@@ -2,7 +2,7 @@
 % function [Dout,TrialTime,nUnits,nTrial,Condition,Area] = Double(Din,opts)
 %
 % Convert a double array to the standard format for the NeuralEmbedding
-% class.
+% class. Double input is interpreted as MUA spectral estimation activity. 
 %
 % Input:
 %   Din (double): Input data in the format nUnits x TrialL x nTrials
@@ -22,7 +22,7 @@
 optsDefault = structfun(@isempty,opts,'UniformOutput',false);
 
 % TODO check for fs
-if ~optsDefault.fs
+if optsDefault.fs
     error('fs field is missing in opts structure.\nIt is required when converting data from double format.\nPlease input the sampling frequency (in Hz) in opts.fs.');
 end
 

+datareader/+is/Double.m

@@ -45,7 +45,7 @@ function ValidateArgs(Din,opts)
 %       area (string): Area labels ( 1 x nUnits )
 %       condition (string): Condition labels ( 1 x nTrials )
 %
-
+optsDefault = structfun(@isempty,opts,'UniformOutput',false);
 [nUnits,Time,nTrials] = size(Din);
 
 % Checks if the time vector matches the input data second dimension

+datareader/+is/Struct.m

@@ -94,7 +94,7 @@
     % If required field is not present, checks in opts 
     for ff = [fields2check; fieldType]
         % retrieve the correct fieldname between those accepted
-        thisFieldName = fnames(ismember(fnames,datareader.is.Struct(ff(1))));
+        thisFieldName = fnames(find(ismember(fnames,datareader.is.Struct(ff(1))),1,'first'));
         if isempty(thisFieldName) && optsDefault.(ff(1))
             error("No field %s provided in opts struct.\n",ff(1));
         elseif ~isempty(thisFieldName) &&...