Finding the equation from a set of numbers

Old_Trafford · 2011-07-04 00:18:17

Hello all,

nice to join this forum.

I have a question about maths. I want to create an equation from data values. The equation should be something like A=B+k*C
I have a set of values for A, B and C and i want to connect them in order to find k. Which software should i use for that?

Thank you very much.

bobbym · 2011-07-04 00:19:26

Hi Old_Trafford;

Welcome to the forum!

Paste the data into a post and I will fit it for you.

Old_Trafford · 2011-07-04 00:20:49

Hello Mr. BobbyM

the data is huge and i cannot post it. Can you please tell me a methodology, so i can do it in the future again?

Thank you very much!

bobbym · 2011-07-04 00:26:05

Hi;

You will need a program to do the fit for you. That would mean learning a complicated program.

Old_Trafford · 2011-07-04 00:27:14

Can you please suggest a program? I am good at learning software, and i would like to learn one powerful program.

If you cannot tell me a program here, please ''private message'' me.

Old_Trafford · 2011-07-04 00:28:40

I know how to use Matlab and Mathematica, but only for specific jobs. Can any of those two do the job?

bobbym · 2011-07-04 00:29:41

R should be able to do it. Sage can do it.

Mathematica, Maple and Derive can do it easily but they cost money.

Old_Trafford · 2011-07-04 00:31:44

Which program would you use to do it for me before?

Is it easy to tell me the method so that i can do it?

We already own mathematica, and the other two are free(R and Sage).

bobbym · 2011-07-04 00:37:21

Curve fitting requires you solve a big set of simultaneous equations at the very least. If you have a lot of data it can not be done by hand. I would use Mathematica or Maple because I am familiar with them.

Old_Trafford · 2011-07-04 00:38:05

Can you please tell me how to do it in Mathematica?

bobbym · 2011-07-04 00:45:12

It is a single command:

This is some mock data:

data={{1,3,8},{2,5,13},{3,8,17}}

Fit[data,{1,b,c},{b,c}]

This is the result.

a= 7 b- c+4

Old_Trafford · 2011-07-04 00:53:39

Thank you very much, i will try it now and see if it worked.

Thanks for your time

bobbym · 2011-07-04 00:57:50

It will be a little bit more complicated then that, You will have to do some alignment with your data. Come back if you have a problem.

Old_Trafford · 2011-07-04 00:59:00

ΟΚ i will try and come back if any problems occur

bobbym · 2011-07-04 01:03:09

Hope it goes okay. But if not I will try to help.

Old_Trafford · 2011-07-07 03:42:50

I get this message:

Fit::fitd: First argument {{5.463`,5.271`},{2,5,13},{3,8,17}} in Fit is not a list or a rectangular array.

Can you imagine what is problem?

I have the excel file and i could send it to you, so you can also try to do it(if you have available time).

Old_Trafford · 2011-07-07 03:49:38

508.463 29.8554 33.3831
515.271 29.8752 33.5417
522.866 29.9544 33.6408
A B C

The first column is 3 values of A, the second is three values of B and the third is three values of C

Old_Trafford · 2011-07-07 03:53:48

how am i supposed to enter these into mathematica?

Old_Trafford · 2011-07-07 04:00:00

I remind you that i want an equation of this format: A=B+k*C , mainly i want to find k, but from inserting 4000 A,B and C values.

Last edited by Old_Trafford (2011-07-07 04:01:54)

bobbym · 2011-07-07 04:11:23

Hi;

Give me a second to examine the output.

Old_Trafford · 2011-07-07 04:12:27

I could make it on excel, finding a linear connection between A,B and C, but i want to make it a little more complicated. I want to use the multiple correlation coefficient, which would also help me find more accurate values.

bobbym · 2011-07-07 04:14:25

Hi Old_Trafford;

One problem at a time. I am still looking at your first questions.

Old_Trafford · 2011-07-07 04:15:44

Hello! Sorry, take your time.

bobbym · 2011-07-07 04:16:45

Here is the first problem:

{{5.463`,5.271`},{2,5,13},{3,8,17}}

The first element {5.463`,5.271`} only has two numbers in it.

Old_Trafford · 2011-07-07 04:18:44

Alright, thats really bad from my part

Math Is Fun Forum

#1 2011-07-04 00:18:17

Finding the equation from a set of numbers

#2 2011-07-04 00:19:26

Re: Finding the equation from a set of numbers

#3 2011-07-04 00:20:49

Re: Finding the equation from a set of numbers

#4 2011-07-04 00:26:05

Re: Finding the equation from a set of numbers

#5 2011-07-04 00:27:14

Re: Finding the equation from a set of numbers

#6 2011-07-04 00:28:40

Re: Finding the equation from a set of numbers

#7 2011-07-04 00:29:41

Re: Finding the equation from a set of numbers

#8 2011-07-04 00:31:44

Re: Finding the equation from a set of numbers

#9 2011-07-04 00:37:21

Re: Finding the equation from a set of numbers

#10 2011-07-04 00:38:05

Re: Finding the equation from a set of numbers

#11 2011-07-04 00:45:12

Re: Finding the equation from a set of numbers

#12 2011-07-04 00:53:39

Re: Finding the equation from a set of numbers

#13 2011-07-04 00:57:50

Re: Finding the equation from a set of numbers

#14 2011-07-04 00:59:00

Re: Finding the equation from a set of numbers

#15 2011-07-04 01:03:09

Re: Finding the equation from a set of numbers

#16 2011-07-07 03:42:50

Re: Finding the equation from a set of numbers

#17 2011-07-07 03:49:38

Re: Finding the equation from a set of numbers

#18 2011-07-07 03:53:48

Re: Finding the equation from a set of numbers

#19 2011-07-07 04:00:00

Re: Finding the equation from a set of numbers

#20 2011-07-07 04:11:23

Re: Finding the equation from a set of numbers

#21 2011-07-07 04:12:27

Re: Finding the equation from a set of numbers

#22 2011-07-07 04:14:25

Re: Finding the equation from a set of numbers

#23 2011-07-07 04:15:44

Re: Finding the equation from a set of numbers

#24 2011-07-07 04:16:45

Re: Finding the equation from a set of numbers

#25 2011-07-07 04:18:44

Re: Finding the equation from a set of numbers

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