function composed from another functions - "solve" does not work

[skjoex]

Hi,

I have a function composed from another 3 functions and I like to obtain points where f(x) = 0. So in attached I expect 4 values, but solve does not work. Please help.

Regards

 

[GregLocock]

In what way does solve not work?




Cheers

Greg Locock


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[skjoex]

GregLocock, did you open the attached ? On my computer when try to "solve" MYY(x) MYY is in red and note sais "This variable is undefined"...or do you see on your computer a result ?

 

[IRstuff]

You might get more responses if you post a Mathcad 11 file

TTFN

FAQ731-376

 

[Occupant]

On my computer when try to "solve" MYY(x) MYY is in red and note says "This variable is undefined"...or do you see on your computer a result ?

That's not what it says on mine: "polycoeff" is not defined, ergo MY(x) is not defined, ergo MYY(x) is not defined.

 

[skjoex]

Occupant, maybe better to post a printscreen in this case, I guess that you have set default value for array origin to zero, I have array origin set to one. And hope you can see clearly, that MYY(x) is plotted so it have to be defined

 

[skjoex]

ok, I helped to myself by brutte force approach, but I am still interested of something more elegant.

 

[PNachtwey]

I would use the minerr function.

Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

 

[PNachtwey]

Oops, or the root function.

Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

 

[Occupant]

The setting of ORIGIN goes with the worksheet, why would I have changed it? "polycoeff" is not a Mathcad function and not defined in the worksheet you submitted, therefore, it creates an error. The obvious conclusion is, you uploaded only a portion of your worksheet. How can you expect to get help with an error that you yourself created by submitting this?

 

[seymours2571]

skjoex,

It maybe that mathCAD's symbolic solve command cannot solve for x when MYY(x) is a function with embedded if/then logic. Either way, pretty impressive worksheet.

Oh..and polycoeff *is* a MathCAD function in my version (v14). Maybe Occupant's conclusion isn't so obvious.

Steve

Stephen Seymour, PE
Seymour Engineering & Consulting Group

http://www.seymourecg.com

 

[Occupant]

Oh..and polycoeff *is* a MathCAD function in my version (v14). Maybe Occupant's conclusion isn't so obvious.

I have to admit, I am not using v14 but v13 and I had to go back to find out. If you're right, how come "polycoeff" turned red (in V14-M020 and V13, of course) and I got "this variable is undefined". If it was a function recognized by Mathcad, I should have gotten "this function does not apply here" or some such thing.

 

[IRstuff]

It's actually part of the Data Analysis Extension Pack, which should have come with Mathcad 14.:

polycoeff(vx, vy) Takes two real vectors of the same length vx and vy and returns the coefficients of the interpolating polynomial function

TTFN

FAQ731-376