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# plotting problem - empty graph

Posted 10 years ago
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Posted 10 years ago
 I do not know why it returned GraphicsComplex instead of Line here. btw, you need to use := not = in the function definition. When asking questions, it helps to post complete self contained code you used all in one cell. This helps someone see what you actually typed. Include all definitions and commands used.
Posted 10 years ago
 This was the code i used for plotting f[x] versus x. f[x_] := ((x - 50000)^4.51846) (E^(50000 - x)) (4.6924*^-7) After typing this, when i entered f[x] the result was 4.6924*10^-7 E^(50000 - x) (-50000 + x)^4.51846 It means the function definition is correct. After this when i wanted to plot f versus x, i used the following commandp= Plot[f, {x, 0, 50000}] I did not get any graph!!! i wanted to know the points. For that i used "data = (InputForm@p)[[1, 1, 1, 3, 2, 1]]". After this the result was, Graphics[GraphicsComplex[{{0.00010204081632653062, 0.}, {98.143306007652, 0.}, {204.54178542729326, 0.},etc... Now Can anyone explain what i should do? I am not able to understand this..
Posted 10 years ago
 Hi, there are several "issues" here. First of all (x - 50000)^4.51846 is complex for x<50000, e.g. (x - 50000)^4.51846 /. x -> 2 is -9.88935*10^19 + 1.70333*10^21 I. Plot does not plot complex numbers.The "interesting part of your graph is for x>50000. Also, you should plot f[x] instead of "f". f[x_] := ((x - 50000)^4.51846) (E^(50000 - x)) (4.6924^-7) Plot[f[x], {x, 50000, 50050}, PlotRange -> All] does work and gives a reasonable output: So, if you plot it for x< 50000 it will not produce a useful output, because the Plot function is not made to plot complex functions. Furthermore, the values that you want to plot are insanely large. Look at this: Table[Evaluate[f[x]], {x, 0, 5}] {-1.046106944790515*10^21730 + 1.801802763355185*10^21731 I, -3.848064616838928*10^21729 + 6.627862949115713*10^21730 I, -1.415495933981097*10^21729 + 2.438034178117325*10^21730 I, -5.206847948258534*10^21728 + 8.968215982373779*10^21729 I, -1.915319207666480*10^21728 + 3.298924128423410*10^21729 I, -7.045428821964528*10^21727 + 1.213496687279907*10^21729 I} In the interesting regime 50000
Posted 10 years ago
 Same issue as http://community.wolfram.com/groups/-/m/t/284702 Be aware that clever things like data = (InputForm@p)[[1, 1, 1, 3, 2, 1]] are not guaranteed to be the same in different versions.