Re: Plot function with two arguments

*To*: mathgroup at smc.vnet.net*Subject*: [mg122115] Re: Plot function with two arguments*From*: "Oleksandr Rasputinov" <oleksandr_rasputinov at hmamail.com>*Date*: Sat, 15 Oct 2011 06:02:27 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j79109$i3b$1@smc.vnet.net>

On Fri, 14 Oct 2011 10:56:25 +0100, Alexei Boulbitch <Alexei.Boulbitch at iee.lu> wrote: > "Remove Evaluate, and all the curves will be the same color." > > Why actually it behaves this way? > > This: > > f[x_, k_] := (k*x^2 - x)/(x - k); > Plot[Table[f[x, k], {k, -3, 3}], {x, -20, 20}] > > indeed yields all lines of the same colour. However, this: > > lst=Table[f[x, k], {k, -3, 3}]; > Plot[lst, {x, -20, 20}] > > returns the lines with different colours. I would appreciate, if one > explains the reason For such a behaviour. > > Thank you, Alexei Plot has HoldAll. By the looks of it, a check is done to see if the first argument has head List; if so, Plot understands that it is being given a list of functions and colours them accordingly. If the Head is not List, though (for example, in this case it would be Table), Plot treats it as a single, vector-valued function, with all branches plotted using the same style.