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kirma
kirma
06:17
I wonder about Mma license pricing. My annual license renewal price seems to differ from listed annual price on the website by about 15% (and that's not taxes)...
 
6 hours later…
Jason B.
Jason B.
12:44
@xzczd I just gave some feedback on the resource functions doc page. Seems fixable
dtn
dtn
12:55
I was busy with numerical differentiation of functions and came across the following.
Remove[f, n, h];

n = 4;

ddddf = 1/h^n Sum[(-1)^(k + n) Binomial[n, k] f[x + k h], {k, 0, n}];

h = 0.0001;

f[x_] := 1/10 Sin[3 x] Exp[-x] x;

Plot[{f[x], ddddf, Evaluate[D[f[x], {x, n}]]}, {x, 0, 5},
PlotRange -> All]
That is for h=0.0001. I guess that this may be due to the step with the accuracy of the calculations, but the deep essence of the phenomenon is unknown to me. Can someone please explain this.
user image
For high-order approximation of derivative I use this formula:
user image
xzczd
xzczd
@JasonB. Happy to hear that! Hope it can be fixed soon.
 
5 hours later…
JimB
JimB
17:47
@dtn Adding WorkingPrecision -> 4 (or higher than 4) to the Plot command and changing h to h = 1/10000 and putting that updated value of h before ddddf fixes the display. Also, f[x] is much, much smaller than the other two (essentially identical) functions so it looks flat on the figure.

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