Error using LTSpice2Matlab function

I am using the LTSpice2Matlab function to extract the values of some variables and use them in Matlab. The command:

data= LTspice2Matlab('netlist_whole_network.raw'); Format error in LTspice file "C:\Users\...\netlist_whole_network.raw" ... Bad tag name found!

Could you tell me the reason for this error and how can it be rectified? Also, what is a tag?