I've been comparing the 'plot' command with direct calls to gnuplot. The following lines generate a plot of radial, hoop and max shear stress in a compound cylinder:

operator SIGR; let {SIGR(~r) => E1/(1-nu1)*(c1*(1+nu1)-c2*((1-nu1)/r^2)) when numberp r and r<c, SIGR(~r) => E2/(1-nu2)*(c3*(1+nu2)-c4*((1-nu2)/r^2)) when numberp r and r>c}; operator SIGH; let {SIGH(~r) => E1/(1-nu1)*(c1*(1+nu1)+c2*((1-nu1)/r^2)) when numberp r and r<c, SIGH(~r) => E2/(1-nu2)*(c3*(1+nu2)+c4*((1-nu2)/r^2)) when numberp r and r>c}; operator TAUMAX; let TAUMAX(~r) => (max(SIGR(r),SIGH(r))-min(SIGR(r),SIGH(r)))/2 when numberp r; load_package gnuplot$ plotreset; % reset the plot subsystem; gnuplot(set,key); plot(SIGR(x),SIGH(x),TAUMAX(x),x=(a .. b),title="plot_title",output="plot_2");

c1 through c4 are coefficients from solving a system of eqns; a = inner radius, b = outer radius and c = contact radius.

I have not found a way to show a key (legend) with the plot command. Direct calls to gnuplot produce a key, but I don't understand how to pass my operators in reduce to gnuplot. I consulted the "Gnuplot Interface for REDUCE Version 4" document by Herbert Melenk, but that did not shed any light on this. Is it possible to produce a key usin 'plot' or pass operators directly?