Equation for a surface (i.e.an equation for 2 variables)

[Guest]

I would like to find an (approximate) equation for a table that has 2 variables. example: z = function of (x and y)

I can find the equation using trendline after making a 2 dimensional graph, but do not know how to do this for an additional variable.

 

[Kevin Stecyk]

Rod,

If I understand you correctly, you are simply solving simultaneous
equations.

You can also solve simultaneous equations using Solver. The target cell must
be given a value (usually =1 will do). Then the constraint equations are the
linear simultaneous equations that you want to solve.

Here are some links that might help you. Interestingly, Ray Steele has set
up a template to help solve 10 unknowns.

http://www.frontsys.com/tutorial.htm

http://ray.steele.org/excel.htm

Come back with any questions you have.

Best regards,
Kevin

I would like to find an (approximate) equation for a table that has 2

variables. example: z = function of (x and y)

I can find the equation using trendline after making a 2 dimensional

graph, but do not know how to do this for an additional variable.

 

[Jerry W. Lewis]

If the function is a linear combination of x and y, then you can use
LINEST to get least squares estimates of the coefficients. Help for
LINEST is misleading, because the early paragraphs leave the mistaken
impression that the predictor variable must be a single column.

Jerry

 

[Bernard V Liengme]

Hi Rod,
Send me the data and I will show you how to use LINEST.
Bernard
www.stfx.ca/people/bliengme

I would like to find an (approximate) equation for a table that has 2

variables. example: z = function of (x and y)

I can find the equation using trendline after making a 2 dimensional

graph, but do not know how to do this for an additional variable.