read multiple data from arduino serial monitor to matlab

I have successfully read the temperature from my thermocouple in the arduino and connected it in the matlab by displaying the value using tis command:

clear all

s = serial('com4');

fopen(s);

i = 1;

while(1)

data(i)= str2double(fscanf(s));

plot(data);

title('Temperature Monitoring')

xlabel('Time')

ylabel('Temperature')

pause(15);

i=i+1;

end

now i want to use more than 1 thermocouple to display in the matlab. How do I do it and how to differentiate between thermocouple 1,2 or more than that?