Re: Why don't my plots appear? My 5.2 code no longer works

*To*: mathgroup at smc.vnet.net*Subject*: [mg89342] Re: [mg89326] Why don't my plots appear? My 5.2 code no longer works*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Sat, 7 Jun 2008 02:50:40 -0400 (EDT)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*References*: <200806061044.GAA24071@smc.vnet.net>*Reply-to*: murray at math.umass.edu

You'll probably get zillions of responses to your question. The treatment of Plot and related functions has changed with version 6: the graphic created is no longer a side-effect of evaluating the function, but rather the actual, direct RESULT of the function. (In Mathematica 5 and before, the display was a side-effect whereas the direct result was a -Graphics- object.) A consequence is that following a Plot with a semi-colon now has EXACTLY the same effect of following any other command with a semi-colon: it suppresses the result. More precisely, it produces a Null result, which by default is not shown in any way. In general, a semi-colon is used to separate the parts of a compound expression, for example: a = 2; Plot[Sin[a x], {x, 0, Pi}]; "Hello, world!" (* NO! *) has result the string 'Hello, world!. And indeed in Mathematica 6 you the semi-colon after the Plot expression appears in red to warn you. To make the plot appear, use Print: a = 2; Print[Plot[Sin[a x], {x, 0, Pi}]]; "Hello, world!" (* Yes *) Note this has nothing to do, per se, with Modules -- just compound expressions in general. Charlie Brummitt wrote: > Hello, > I am running into difficulties with Plot. Some code of mine that worked in > 5.2 no longer works correctly in 6.0.2.0. Specifically, no plots appear > whenever Plot (or Plot3D or DensityPlot or ListPlot) is called within a > function that I have defined. > > Here is a closely related question: What does the red semicolon ";" mean at > the end of "Plot[ ... ];"? Why is it red? In 5.2, placing a semicolon at the > end of Plot[] allowed me to output a plot in the middle of a computation, > without halting the computation. Now I can no longer seem to output a plot > in the middle of a long computation. (I only see the output of Print[] > commands.) I must be able to see these plots during long computations, like > I was able to in 5.2. > > What's wrong? Can anyone please help? > > Thanks, > > Charlie > > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305

**References**:**Why don't my plots appear? My 5.2 code no longer works correctly in 6.0***From:*"Charlie Brummitt" <cbrummitt@wisc.edu>