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Re: Plotting a function -


Craig Reed wrote:
> Hi -
> 
> I'm trying to get Mathematica 5.2 to graph a function which is the ratio of 
> integers which have a '3' in them. Done in Exce3l, the graph of the first 
> 32,000 data points has a fractal look to it, especially when done with a 
> log scale.
> 
> What I've tried is the following
> 
> 
> f[x_] := Boole[DigitCount[x, 10, 3]]
> g[x_] := Sum[f, {i, x}]/x
> Plot[g, {x, 1, 100}]
> 
> 
> I get 3 errors of "g is not a michine-size real number at" followed by 3 
> real numbers:
> 1.000004125
> 5.016125.....
> 9.39607.....
> 
> What am I doing wrong?  or perhaps what I should ask is, "Is there a better 
> way?"
> 

The following version of your code should give you the expected graph:

f[x_] := Boole[DigitCount[x, 10, 3] > 0]
g[x_] := Sum[f[i], {i, x}]/x
Plot[Evaluate[g[x]], {x, 1, 100}];

Regards,
Jean-Marc


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