my_funcI(){
        grep 'mystring' I.dat
}
my_funcQ(){
       grep 'mystring' Q.dat
}
myfuncI
myfuncQ

my_func(FILE){
      grep 'mystring' ${FIlE}.dat
}
my_func(I)
my_func(Q)

#!/bin/sh

my_func()
{
        grep 'mystring' $1
}

my_func  I.dat
my_func  Q.dat

#!/bin/sh

my_func()
{
        grep 'mystring' $1.dat
}

my_func  I
my_func  Q

I_plt=/tmp/I_out.plt$$
Q_plt=/tmp/Q_out.plt$$
 
plot(){
  echo "#!/usr/local/bin/gnuplot -persist" > $1_plt
  echo "plot \"$1_indat.txt\" " >> $1_plt
  
 }

  plot I
  cat $I_plt 
  plot Q
  cat $Q_plt