load matrix with variable from text file using fileread

Hi I have a matrix eg :

[ 1 2 3 J

4 5 6 J];

I want to load this into matlab but the letter turns into NaN, i want to import the matrix into matlab then herafter ( in Matlab) define/give a value to ( J )

eg:

J = 2

I have used fileread, which is good for numbers, but turns letters to NaN

[Giuseppe Inghilterra]

Can you attach a txt file sample? When I use fileread on my own I obtain a character vector and I don't have the behaviour (NaN values) that you have described.