Matrix Math Puns

I went here for undergrad and now for phd and I feel like I can't do any linear algebra whatsoever. Could be my fault but I also feel like they give us little help with math 225. I'm very curious about the general sentiment among engineering people. (Math people... I am hoping you had a better experience.)

Note: if you're one of the couple people I've been complaining to about lin alg all day today, I'm sorry you had to see it on reddit too. :| I'm a whiner

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I got tired of hacking together simple matrix multiplication every time it came up, so I finally bit the bullet and made a comprehensive matrix math library for TwinCAT 3: TcMatrix.

I've used the siemens matrix functions before, and I was able to find a codesys library when googling that seemed pretty similar. Is anyone here familiar with matrix libraries for other platforms? I'd love to evaluate them and compare features.

This was also kind of an excuse to play around with dynamic memory allocation in TwinCAT and the TcUnit framework. Both were a lot easier than expected, so I think I might use them more in the future and encourage others to use them as well!

I have a few other libraries in the works, so any other style or documentation feedback would definitely be appreciated! The one thing I wish I could figure out is how to export the in-code documentation from TwinCAT so I wouldn't have to document everything twice :/

I suppose it's technically table operations rather matrix operation but same idea: I want to mark dates without explicitly typing each date.

Say I create a table using a variable:

Cyber Monday =

var cm_dates = {Date(2021, 11, 29), Date(2020, 11, 30), Date(2019, 12, 02)}

... And I want to look at 7 days before, the day of, and 7 days after each Cyber Monday of their respective year. So the day after row would be 2021-11-30, 2020-12-01, ans 2019-12-03 and then day before row would be 2021-11-28, 2020-11-29, and 2019-12-01.

Continuing and doing either of the below don't work:

--attempt 1

RETURN Switch(true(),

Calendar[CalendarDate] IN cm_dates, t0 -- this line is fine

Calendar[CalendarDate] IN dateadd(cm_dates, 1, day), t1, -- this does not

Blank() )

--attempt 2

RETURN Switch(true(),

Calendar[CalendarDate] IN cm_dates, t0 -- this line is fine

Calendar[CalendarDate] IN dateadd(cm_dates, {1,1,1}, day), t1, -- this does not

Blank() )

The formulas, if they worked, would have more rows so that itd range from 14 and - 14 based on cm_dates, but since it doesn't I just kept it like this for brevity.

Im drawing a blank here.

Any ideas?

Editted the DAX part for readability

First post here!

Date and Time: 10/29/21 11:00 UTC.

For more info, send DM.

Will provide with exam scope, and some handouts to check on.

Suppose I want to render a mirror in a scene. I have my view mat4 and the model mat4 for some mirror plane. I need to create a new view mat4 that is reflected about that plane to render objects reflected in the mirror. For some reason I can't find any description of how to create is new matrix - I tried adapting code from this portal tutorial and simply using the same object matrix for src and dst (i.e. the plane is a portal to itself) but doing so creates a view matrix that seems to be oriented incorrectly for a mirror.

What's the trick to getting the matrices to render a mirror?

I tried this (code uses GLM, camView is the regular camera view matrix and node.getCachedWorldTransform() gets the model matrix of the mirror plane):

            auto pCam = camView * glm::inverse(node.getCachedWorldTransform()) * glm::rotate(glm::mat4{ 1.0f }, glm::radians(180.0f), glm::vec3(1, 0, 0))  * node.getCachedWorldTransform();

But it does not seem to work, nor do variations that more closely match the OpenGL wiki tutorial

From the matrix below, there exist infinitely many solutions to be written the given form, also below. I have to find this equation for solutions where λ and μ are real numbers, and I’m struggling on where to start with such a large matrix. I’ve tried on smaller (3x4) matrices, by substituting in a value for the variable not given (z in that case) but I’m unsure how to approach this question. Do I substitute more values in? Altogether or one at a time? I’ve broken it into the 3 simultaneous equations already.

Matrix

Form

I tried to solve it with many methods still same answer You can see the question and my answer in the pic Plus what does he mean by matrix without hyphen(I think he means the horizontal line in matrix)

I tried with Cramer and it give : X1= -202/13 X2= 29/13 X3= -5/13
Still wrong

https://imgur.com/a/F1DOtJD

If anybody got any idea this would be a big help

Was pretty early like 20ish. Was it literally just adding each place that corresponds?

Hi- so I know how to solve simultaneous equations in matrix form but I had my first period of my SAC today (Australian assessment) and noticed that the two last problems I need to first write simultaneous equations in algebraic form which I have really struggled with. I have my last hour to work on it tomorrow. I try to write them out but it never makes sense because I cant use the process of elimination or substitution on them. Because it is an assessment I don't have the questions but I can do a random example:

(I know it was about basketball tickets) "Non-members and members pay a different amount for a ticket at a basketball game but it also depends on the round of basketball Round 1 Non members pay $37 Members pay $23 Round 2 Non members pay $46 Members pay $35, Round 1 totalled $5487 and round 2 totalled $3567 how many tickets were sold (im not sure exactly of the question)"

What I am struggling with is actually putting this into an equation form not matrix form. I had an idea that I could go based off of my matrix form and just kind of deconstruct (work backwards)

Thank yall so much

There was a question about matrices where it was like -4 times the 4x4 matrix. was the answer matrix just -4 multiplied by each of the numbers in the matrix?

Hi, I'm looking for someone to help me with math tutoring / problems.

It's mostly diff equations and matrix algebra.

If interested please send me your rates.

Thanks! :)

$50-100 per session

If anyone uses VBA to do complex math, I'm working on an object-based VBA Math library. I currently have Matrix and Vector classes implemented.

Beakerboy/VBA-Math-Objects: Object-Based mathematical operations in VBA (github.com)

I've used these objects to create a Principal Component Analysis object as well, in another repository:

Beakerboy/VBA-Projects: Calculate Confidence intervals, Confidence Ellipses, and LOESS Smoothing. (github.com)

I’m not exactly sure, but I think Math 251 I’m taking this summer term is like 4 weeks, 5 days a week. Which is like 20 class days, I know the classes are longer, but still, has anyone taken this version of 251 in the summer and is it doable alongside a light asynchronous gen Ed? A buddy of mine says the class isn’t hard, but still 28 days to learn all that material is crazy.

The Average from The Test is 234 000 Ounces of 201 people votet. That's an average about 1 100 Ounces Silver per person. That means 1 100 Ounces X 51. 500 Apes = Around 60 Million Ounces of Silver - >worth more than 1, 5 Billion dollar ( to 30$per Ounce). If the Price will rise up to 150 Dollar per ounce and at this time 100.000 Apes are buying silver - >

100.000 Apes x 1000 Ounces Per Ape x 150 $ per Ounce = Error - System Failure

1, 5 Trillion Dollar

This will break the matrix and will Change the world Into Planet of The APES!