The key to it is the 'phonging' procedure that we used yesterday to make that cute little sphere. So, here is the code. For ease of use, I defined the values that we want to plot in f1...f7 at the beginning of the file.
reset A=-1 B=7 C=-4 D=3 # These are the actual values to be plotted f1 = 1.0 f2 = 1.3 f3 = 0.4 f4 = 1.5 f5 = 1.9 f6 = 1.1 f7 = 0.9 # Radius of cylinders r = 0.4 # Vertical position of 'phong' point vp = 1.0 unset key unset colorbox set sample 100 set isosample 50, 50 set parametric set urange [0:1] set vrange [0:1] set xrange [A:B] set yrange [C:D] # Basically, this is the definition of our cylinder set table 'test.dat' splot r*sin(2*pi*u), r*cos(2*pi*u), v,\ r*sin(2*pi*u)*v, r*cos(2*pi*u)*v, 1 w pm3d unset table set multiplot set zrange [0:2] unset xtics unset ytics set ztics out set grid ztics set ticslevel 0 # First, we draw the 'box' around the plotting volume set palette model RGB functions 0.9, 0.9,0.95 splot A+(B-A)*u, C+(D-C)*v,0 w pm3d # These are the vertical panes, with a gradient along set palette model RGB functions 0.9, 0.9, 0.7+gray/5.0 splot A, C+(D-C)*u, 2*v w pm3d, A+(B-A)*u, D, 2*v w pm3d set border 1+2+4+8+16+32+64+256+512 f(x,a,b) = 0.9*exp(-(x-a)*(x-a)/b/b) set palette model RGB function gray, gray, 1 sp 'test.dat' u 1:2:($3*f1):(f($3*f1,vp,0.8)*f($1,0.3,0.2)*f($2,-0.3,0.2)) w pm '' u ($1+1):2:($3*f2):(f($3*f2,vp,0.8)*f($1+1,1.3,0.2)*f($2,-0.3,0.2)) w pm3d,\ '' u ($1+2):2:($3*f3):(f($3*f3,vp,0.8)*f($1+2,2.3,0.2)*f($2,-0.3,0.2)) w pm3d,\ '' u ($1+3):2:($3*f4):(f($3*f4,vp,0.8)*f($1+3,3.3,0.2)*f($2,-0.3,0.2)) w pm3d,\ '' u ($1+4):2:($3*f5):(f($3*f5,vp,0.8)*f($1+4,4.3,0.2)*f($2,-0.3,0.2)) w pm3d,\ '' u ($1+5):2:($3*f6):(f($3*f6,vp,0.8)*f($1+5,5.3,0.2)*f($2,-0.3,0.2)) w pm3d,\ '' u ($1+6):2:($3*f7):(f($3*f7,vp,0.8)*f($1+6,6.3,0.2)*f($2,-0.3,0.2)) w pm3d unset multiplot
If you look at it, this code is really nothing more than what we have already seen in previous days: apart from the general set-up commands, we plot the cylinder first to a file, (this time, we put on the cap, too), then draw the box in which we plot the bars. To make it more interesting, the vertical panes are given some gradient. You can check out the details of this in my previous post.
Finally, the cylinders are plotted one by one. Each time a new cylinder is processed, we shift it to the right, so that it doesn't overlap with the previous ones. To make the cylinders 3D-looking, we add the phong, as we discussed it yesterday. If you find that the white spot (actually, it is not completely white, but some very faint shade of blue, some steel-like colour) is too tight, you can ease up a bit on the Gaussian function. You can also shift the vertical position of the centre of the spot by tampering with the value of 'vp', somewhere at the beginning.
Again, it shouldn't be a problem to script the whole procedure. Once I have some time, I will do that and post it here. Till then!