# Exponential plot

Hello,
I want to plot the exponential function for +ve and -ve value of [0] on the same graph. How can I do this without defining another new function?

TF1 *f0 = new TF1(“f0”, “exp(-[0]*x)”, -4,4);
f0->SetParameter(0,0.5);
f0->Draw();

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I’m not sure what you really want …

… maybe this …

`Double_t ve = 4.; f0->SetRange(-ve, ve); f0->Draw();`

… or maybe this …

``````Double_t ve = 4.;
f0->SetParameter(0, ve); f0->DrawCopy("L");
Int_t n = 10;
for (Int_t i = -n; i < n; i++)
{ f0->SetParameter(0, i * (ve / n)); f0->DrawCopy("L SAME"); }
``````

… or maybe that …

``````Double_t x = 4., y = 4.;
TF2 *f = new TF2("f", "exp(-x*y)", -x, x, -y, y);
f->Draw("surf2 z");
``````

If I have function like exp(-kx). I want to plot for +ve and -ve value of k in the rang (-4,4).

If I apply above code, it just update the latest value of the SetParameter. I only get onside of the curve (either +ve k or -ve k).

Hope I made the question clear.

I mean I wanted to update the plot with new SetParameter for the already defined function. Is it possible to do that? In my code, I got the plot with the most recent value of SetParameter ( only one plot, expected plot is two curve).

Maybe:

``````Double_t ve = 4.;
f0->SetParameter(0, -ve); f0->DrawCopy("L");
f0->SetParameter(0,  ve); f0->DrawCopy("L SAME");
``````

Thank you!

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