Add values to a PlotLabel; use text characters for PlotMarkers in DiscretePlot3D

Question

I have a plot like this:

Table[Plot[a*x^2/4, {x, 0, 5}, PlotLabel -> "a="  a], {a, 1, 5, 1}]

I want to label the plots as a=1, a=2, ..., but Mathematica labels them as a=, 2a=, ....

How can I solve this problem?

I also have another problem:

DiscretePlot3D[2 x + y, {x, {1, 4, .2}}, {y, {2, 6, .2}}, 
   Filling -> None, PlotMarkers -> {"Sphere", .01}]

Why I can not use plot markers such as *, \[FilledSquare], ... in this plot?

Answer 1

The PlotLabel needs to be a string, so for instance:

 Table[Plot[a*x^2/4, {x, 0, 5}, PlotLabel -> "a=" ~~ ToString[a]], {a, 1, 5, 1}]

Answer 2

1. Use StringForm[]:

   Table[Plot[a*x^2/4, {x, 0, 5}, PlotLabel -> StringForm["a=`1`", a]], {a, 1, 5, 1}]
   

2. You could make a substitution into the plot graphics object to solve the problem:

   DiscretePlot3D[2 x + y, {x, {1, 4, .2}}, {y, {2, 6, .2}}, 
                  Filling -> None, PlotMarkers -> "Point"] /. 
   Point[pts : {__?VectorQ}] :> (Text["\[FilledSquare]", #, {0, -1}] & /@ pts)