Recent content by AntsyPants

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    Injective and Surjective linear transformations

    Yes I assumed they were of the same dimension, otherwise it wouldn't be invertible, but I have a problem with your statement. Consider for instance the projection T(x,y) = (x,0) T receives a bidimensional vector and also returns one, soT:R^{2}→R^{2}. The spaces are of the same dimension, but...
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    Injective and Surjective linear transformations

    I was struck with the following question: Is there a linear map that's injective, but not surjective? I know full well the difference between the concepts, but I'll explain why I have this question. Given two finite spaces V and W and a transformation T: V→W represented by a matrix \textbf{A}...
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    Fourier Transform vs z Transform

    First of all, seeing we're obviously discussing discrete signals let's make a few things clear. The Fourier Transform of a 1D signal can be defined over \mathbb{R}, unlike the Discrete Fourier Transform which results in a discrete function. On the other hand, the Z-Transform is a function...
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    Finding and recognizing infeasible Lagrange multiplier points

    These problems are rarely straightforward. First of all, you shouldn't solve a problem in a certain way just because it's how it's usually done. That usually means you don't understand what you're doing. If there is a solution to this optimization problem then there must be a set of...
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    What Constitutes an Euclidean Space in Multivariable Calculus?

    I see your point, but you still need to define a norm or else the space isn't metric, so saying it an euclidean space is by definition \mathbb{R}^n still isn't correct. However, based on what you said, if you define a norm in \mathbb{R}^n then the space is instantly euclidean, regardless of the...
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    What Constitutes an Euclidean Space in Multivariable Calculus?

    Feel free to correct me, but saying Euclidean space is by definition \mathbb{R}^n may be a bit of an abuse. \mathbb{R}^n is a vector space generated by the span of n linearly independent vectors also with dimension n. This space, however, needn't be Euclidean as on its own it lacks an inner...
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    Procrustes Analysis and Lagrange Multipliers

    OK I solved this, so I might as well share it with everyone else. First of all, for convenience, I changed the constraint to R RT=I, which is completely equivalent. So the problem is as follows: Maximize tr{R_{xy}R^{T}} subject to R R^{T}=I The solution: First of all, we can...
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    Procrustes Analysis and Lagrange Multipliers

    I'll try this tomorrow, but it will most likely give the desired result. However, why are we given such freedom of defining a new matrix product that's more suitable to the problem? Or is it that in these types of constraints this alternative product must be used? Do you know of any...
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    Procrustes Analysis and Lagrange Multipliers

    The problem: Minimize tr{RyxR} subject to RTR=I This problem is known as Procruses Analysis and can be solved using Lagrange Multipliers, so there's a tendency to write the following function: L(R) = tr{RyxR} - \Lambda(RTR-I), where \Lambda is a matrix of Lagrange Multipliers However, there...
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