Concatenate a string with a variable?

[hswan (Herbert Swan)]

I want to annotate a Plot3D or a Plot with the clause:

PlotLabel-> "c=" <> c

where c is a variable that has been assigned a numeric value. I get the error message,

StringJoin::string : String expected at position 2 in c = <> 150.

I have tried several other syntaxes, to no avail:

PlotLabel-> StringJoin["c=", c]
PlotLabel->"c=" <> StringForm[c]
PlotLabel-> StringJoin["c=", InputForm[c]]

Does anyone know know to do this in Mathematica?

[mthiel (Marco Thiel)]

What about this?

c = 0.3;
Plot[Sin[c x], {x, 0, 20}, PlotLabel -> "C=" <> ToString[c]]

Cheers,

M.

[hswan (Herbert Swan)]

Thank you very much!

[Vitaliyk (Vitaliy Kaurov)]

Marco is precise, this is the way. A small note for the future. PlotLabel formats as TraditionalForm so if you need advanced blend of strings and typesetting you could use Row:

Plot[Sin[3 x], {x, 0, 20}, PlotLabel -> Row[{"C=", Integrate[f[x] BesselJ[x, Pi], {x, a, b}]}]]