gnuplot to plot values of a line of data

[alvaro]

hello

I do not know how to do the following.

I have a .dat file with only a line of data, for example
27 48 12 49 85 12 40.

Could I make a graph with points joined by a line using some of the values of the line on the y axis and arbitrary values on the x axis for example with the points x=10,y=48 x=31,y=85 and
x=36,y=12?

I would like to do it only using the gnuplot commands without
creating a new file with the appropriate columns.

Thanks in advance [;)]