If I use the following  =IF(LIKE(Fields!Symbol, "1tBRN"), Fields!closeval, 40 ) as a data value against the following data I get a nice chart:

date	Symbol	closeval
Type	Text	Text	Double
	04-12-2015	1tBRN	57.86
	04-13-2015	1tBRN	57.93
	04-14-2015	1tBRN	58.43
	If I use the dame formula against mixed data	date Symbol closeval Type Text Text Double 04-12-2015 1tBRN 57.86 04-12-2015 1tWBS 51.52 04-13-2015 1tBRN 57.93 04-13-2015 1tWBS 51.91 04-14-2015 1tBRN 58.43 04-14-2015 1tWBS 53.29 04-15-2015 1tBRN 60.32
		I get : An error occured during the web part rendering. The error was: Pivot processing failed during: Phase: Processing Pivot - Data Matrix - Properties, Action: Evaluating - =IF(LIKE(Fields!Symbol, "1tWBS"), Fields!closeval, 45 ). Error was: Unable to cast object of type 'Nevron.FormulaEngine.NVariant[]' to type 'System.IConvertible'.

The Fields!Symbol reference returns an array. The LIKE function convers that array to Boolean values. However the IF function requires that the passed value is convertible to Boolean. You need to refactor the expression as either:

=IF(FIRST(LIKE(Fields!Symbol, "1tBRN")), Fields!closeval, 40 )

or even better:

=IF(LIKE(FIRST(Fields!Symbol), "1tBRN"), Fields!closeval, 40 )

Best Regards,
Nevron Support Team

Super .So if I then wanted to add a second value to display data from the 1tWBS symbol I could then use then use:

=IF(LIKE(LAST(Fields!Symbol), "1tWBS"), Fields!closeval, 40 ) ?

We are not familiar with your category data groupings -> you perhaps need to first group the data by Fields!Symbol and then make some statistics on it.

Best Regards,
Nevron Support Team