## Search found 6 matches

- Tue Mar 11, 2008 1:07 pm UTC
- Forum: Mathematics
- Topic: Running a system of equations backwards
- Replies:
**10** - Views:
**1973**

### Re: Running a system of equations backwards

What is the size of d, and can you give some idea of what it represents or maybe what you would look for in a "good" C? C is 1x5, x is 5x1, d is 1x1. C is a list of arguments to functions. The output of the functions is defined as argument * the appropriate value in x (since we've just so...

- Mon Mar 10, 2008 8:14 pm UTC
- Forum: Mathematics
- Topic: Running a system of equations backwards
- Replies:
**10** - Views:
**1973**

### Re: Running a system of equations backwards

http://en.wikipedia.org/wiki/Invertible_matrix http://en.wikipedia.org/wiki/Least_squares ? While I understand very little on those two pages, I'm already using least squares to determine x. If it's supposed to help me determine one or more values of C, you'll have to tell me how, because I don't u...

- Mon Mar 10, 2008 3:02 pm UTC
- Forum: Mathematics
- Topic: Running a system of equations backwards
- Replies:
**10** - Views:
**1973**

### Re: Running a system of equations backwards

OK, I think I'm most of the way there. I've solved Ax = b, and got my set of coefficients for the functions x. If I've understood it right, this is step 1. What I now want to do is get the C such that Cx = d, where I specify d (this is the "running it backwards" bit) and reuse x from the f...

- Fri Mar 07, 2008 11:45 pm UTC
- Forum: Mathematics
- Topic: Running a system of equations backwards
- Replies:
**10** - Views:
**1973**

### Re: Running a system of equations backwards

So, because each of your functions is linear and goes from 2-dimensions to 2-dimensions I might be misunderstanding something in your post, but the functions go from 1-dimension to 2-dimensions. So each looks like f(x) = (a1*x, a2*x) presumably. I see your point though, and I can follow your logic ...

- Fri Mar 07, 2008 10:37 pm UTC
- Forum: Mathematics
- Topic: Running a system of equations backwards
- Replies:
**10** - Views:
**1973**

### Running a system of equations backwards

Hi, I'm under the impression that you lot enjoy the sort of maths that makes most of my orifices bleed, so I'm hoping someone will be able to point me in the right direction here. For the "we're not going to do your homework for you" brigade, here's some context: I'm currently doing my fin...

- Fri Mar 07, 2008 9:32 pm UTC
- Forum: General
- Topic: Who the dickens are you?
- Replies:
**10922** - Views:
**2419354**

### Re: INTRO THREAD THE THIRD

Hello. I'm in my final year studying Computing at Imperial College London. I have registered on the xkcd forums to pick the brains of people who are better at maths than me. It's a good excuse to join - I've been tempted to for a while now, and now needs must :D I currently spend too much time playi...