Re: plot function

*To*: mathgroup at smc.vnet.net*Subject*: [mg130307] Re: plot function*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Tue, 2 Apr 2013 03:26:28 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

On 4/1/13 at 1:00 AM, johnandsara2 at cox.net (debguy) wrote: >I can't agree. A semicolon after plot should not stop Show. Below >is straight from the book which i'm sure you've already tried >looking up right ? :) >plot1 = Plot[Sin[x], {x, 0, 2 \[Pi]}, DisplayFunction -> Identity]; >Evaluate the cell to create the graphic. >plot2 = Plot[Sin[2 x], {x, 0, 2 \[Pi]}, DisplayFunction -> >Identity]; >"You can see both graphs together by setting the Show option >DisplayFunction to $DisplayFunction. Evaluate the expression to see >the graphic." >Show[plot1, plot2, DisplayFunction -> $DisplayFunction]; Notice In[1]:= $DisplayFunction Out[1]= Identity So, plot1 = Plot[Sin[x], {x, 0, 2 \[Pi]}, DisplayFunction -> Identity]; is identical to plot1 = Plot[Sin[x], {x, 0, 2 \[Pi]}]; Usage of DisplayFunction in this manner to combine plots went away in version 6 when display of plots ceased to be a side effect. So, with the current version of Mathematica Show[plot1, plot2, DisplayFunction -> $DisplayFunction]; is the same as Show[plot1, plot2]; which will be interpreted by Mathematica as the compound expression Show[plot1, plot2];Null And since Mathematica will only display the result of the last portion of a compound expression, no display results. Also, if you have the default syntax coloring set you will notice the final semicolon in both Show[plot1, plot2, DisplayFunction -> $DisplayFunction]; and Show[plot1, plot2]; is colored red warning you the result may not be as you expect. If you copied your example from a hard copy version of the Mathematica Book, you should be aware the last printed version of that book distributed by Wolfram for Mathematica was for version 4. The substantial changes between version 5 and 6 mean a lot of the graphics examples in the last printed version of the Mathematica book are simply not applicable to the current version of Mathematica. If you copied your example from the online book in version 6 or later, then you found something in the online documentation that Wolfram failed to update. Appending a semicolon to the end of Show[...] should suppress the display. Anything else would mean Show would behave in a manner inconsistent with all other functions in Mathematica. The only function that will produce a display when terminated with a semicolon is Print. And this is because Print sends its output to $Output rather the Out stack.