hardt8
(Nino Hardt)
1
Integrating over x on a Normal-PDF, I expect the answer to simplify to mu.
However, this does not seems to work:
FullSimplify[Integrate[(1/(s*Sqrt[2*Pi]))*exp[-0.5*(((x-m)/s)^2)], x], s \[Element] Reals \[And]s>0\[And]x\[Element] Reals\[And] m \[Element] Reals]
What am I forgetting?
(for convenience: mu is abbreviated m, sigma is abbreviated s)
Try:
FullSimplify[
Integrate[(1/(s*Sqrt[2*Pi]))*Exp[-1/2*(((x - m)/s)^2)], x],
s \[Element] Reals \[And] s > 0 \[And] x \[Element] Reals \[And]
m \[Element] Reals]
(*-(1/2) Erf[(m - x)/(Sqrt[2] s)]*)
Integrate[(1/(s*Sqrt[2*Pi]))*Exp[-1/2*(((x - m)/s)^2)], {x, -Infinity, Infinity}, Assumptions -> {s > 0, m > 0}]
(* 1 *)
Integrate[(1/(s*Sqrt[2*Pi]))*Exp[-1/2*(((x - m)/s)^2)], {x, 0, Infinity}, Assumptions -> {s > 0, m > 0}]
(*1/2 (1 + Erf[m/(Sqrt[2] s)])*)
hardt8
(Nino Hardt)
3
Capital E on exp, of course. Ouch. Thank you.
Also: How 0.5 vs 1/2 results in different output.
So this returns mu:
FullSimplify[
Integrate[x*(1/(s*Sqrt[2*Pi]))*Exp[-1/2*(((x-m)/s)^2)], {x, -Infinity, Infinity}],
s \[Element] Reals \[And]s>0\[And]x\[Element] Reals\[And]
m \[Element] Reals]
Looks different, but answer is the same.
Try:
Integrate[
x*(1/(s*Sqrt[2*Pi]))*Exp[-0.5*(((x - m)/s)^2)], {x, -Infinity,
Infinity}, Assumptions -> {s > 0, m > 0}]
f[m_] := m; Table[
Plot[{Evaluate[INT] // Re, f[m]}, {m, 0.01, 10},
PlotStyle -> {Black, {Dashed, Red}},
PlotLegends -> {"integral with 0.5 not 1/2", "f[m]"}], {s, 1, 10, 1/2}]
(*s from: 1 to 10 and m from: 0.01 to 10*)