430 reputation
27
bio website
location Canberra, Australia
age 27
visits member for 2 years, 5 months
seen Feb 18 at 0:19

Hi,

Generally, I am interested in economics, mathematics (theoretical and applied), statistics (theoretical and applied), and computer programming. I am fluent in Stata, proficient in mata, R, python, and matlab. I occasionally use c++.

Alex


Oct
24
awarded  Yearling
Apr
16
comment If $a_n \rightarrow 1$, does $X_n \overset{p}{\rightarrow} X$ implies $a_n X_n \overset{p}{\rightarrow} X$?
A deterministic sequence is a special case of a random sequence. Each element in the sequence is a random variable with a degenerate (dirac) law.
Apr
14
answered If $a_n \rightarrow 1$, does $X_n \overset{p}{\rightarrow} X$ implies $a_n X_n \overset{p}{\rightarrow} X$?
Apr
3
accepted A special case of integrating over a marginal distribution
Apr
2
revised A special case of integrating over a marginal distribution
added 220 characters in body
Apr
2
comment A special case of integrating over a marginal distribution
Thank you for pointing out that I missed off the $f(z)$. However, I am not sure that the actual fact is wrong. Don't we have $F(x|y) = \int_z F(x|y, z) f(z) dz = \int_z F(x|y', z) f(z) dz = F(x|y')$, where $f$ is the marginal distribution of $z$. The intuition is as follows. By the assumption in the first display $F(x|y, z) = F(x|y', z)$ for all $y, y', z$. Thus if we integrate against the marginal distribution of $z$ on both sides, then equality is preserved.
Apr
2
revised A special case of integrating over a marginal distribution
Added the discrete case.
Apr
2
asked A special case of integrating over a marginal distribution
Feb
24
comment If $A$ and $B$ are $n\times n$ matrices, prove that $|(A^TB)|^2\leq|A^TA||B^TB|$; when is this an equality?
This looks like the Cauchy Schwarz inequality to me.
Feb
21
comment Prove the topology $\mathcal{T} = \{\emptyset\} \cup \{(-\infty, c) | c \in \mathbb{R}\}$ is Tychonoff
Thanks for clearing that up for me!
Feb
21
comment Prove the topology $\mathcal{T} = \{\emptyset\} \cup \{(-\infty, c) | c \in \mathbb{R}\}$ is Tychonoff
Hm, I agree with your intuition @ThomasE.; however, Royden says that "For a continuous mapping $f$ of a topological space $X$ to a topological space $Y$, by the definition of the subspace topology, the restriction of $f$ to a subspace of $X$ is also continuous." The proof is not given. Have I misunderstood this statement? It comes straight after the open set characterization of continuity. I tried to write a proof but the way I tried didn't work.
Feb
21
accepted Prove the topology $\mathcal{T} = \{\emptyset\} \cup \{(-\infty, c) | c \in \mathbb{R}\}$ is Tychonoff
Feb
21
comment Prove the topology $\mathcal{T} = \{\emptyset\} \cup \{(-\infty, c) | c \in \mathbb{R}\}$ is Tychonoff
? = (y-x)/(c-x)? So as $y \to x$, $f(y) \to 0$ and as $y \to c$, $f(y) \to 1$. Then $f$ is continuous on $\mathbb{R}$ with the Euclidean metric and so a restriction of $f$ to this topology is also continuous. But now I wonder about the definition of the Tychonoff separation property on page 227 of Royden/Fitzpatrick.
Feb
21
comment Prove the topology $\mathcal{T} = \{\emptyset\} \cup \{(-\infty, c) | c \in \mathbb{R}\}$ is Tychonoff
Royden's defines a topological space $(X, \mathcal{T})$ to have the Tychonoff propert if "For each two points $u$ and $v$ in $X$, there is a neighborhood of $u$ that does not contain $v$ and a neighborhood of $v$ that does not contain $u$."
Feb
21
asked Prove the topology $\mathcal{T} = \{\emptyset\} \cup \{(-\infty, c) | c \in \mathbb{R}\}$ is Tychonoff
Jan
15
comment Proof that interpolation converges; Reference request
Thanks, very much!
Dec
7
accepted Proof that interpolation converges; Reference request
Dec
7
answered Proof that interpolation converges; Reference request
Dec
3
comment is the function $1/\sqrt{x}$ uniformly continuous?
You're right. I've corrected the answer. Thanks!
Dec
3
revised is the function $1/\sqrt{x}$ uniformly continuous?
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