Group Abstract

Message Boards

WOLFRAM COMMUNITY

4.5K Views

1 Reply

0 Total Likes

View groups...

Follow this post

Share this post:

GROUPS:

Mathematics Algebra Equation Solving Wolfram Language

Intersection point

LUIS ARBOLEDA

LUIS ARBOLEDA, Taller de Mecánica "Cosmos"

Posted 5 years ago

Hi, I was trying to do a program with units. I want to find the intersection point of two functions cau=Quantity[Range[.1,1,.2],"Meters"^3/"Seconds"]; h=Quantity[{100,90,78,64,46},"Meters"]; hs=Quantity[{50,60,72,86,108},"Meters"]; fh=Interpolation[Transpose[{cau,h}]]; (function 1) fhs=Interpolation[Transpose[{cau,hs}]]; (function 2) cau1=cau1/.FindRoot[fh[cau1]==fhs[cau1],{cau1,.1}] Is it possible?

Hi,

I was trying to do a program with units. I want to find the intersection point of two functions

cau=Quantity[Range[.1,1,.2],"Meters"^3/"Seconds"];
h=Quantity[{100,90,78,64,46},"Meters"];
hs=Quantity[{50,60,72,86,108},"Meters"];

fh=Interpolation[Transpose[{cau,h}]];          (*function 1*)
fhs=Interpolation[Transpose[{cau,hs}]];      (*function 2*)

cau1=cau1/.FindRoot[fh[cau1]==fhs[cau1],{cau1,.1}]

Is it possible?

POSTED BY: LUIS ARBOLEDA

1 Reply

Sort By:

Gianluca Gorni

Gianluca Gorni, University of Udine

Posted 5 years ago

Just my guess: `Interpolation` and `InterpolatingPolynomial` are not (yet?) compatible with physical units. The documentation for `QuantityVariable` shows an example of `DSolve` with units: DSolve[{Derivative[1][QuantityVariable[x, "Length"]][ QuantityVariable[t, "Time"]] == Quantity[5, "Meters"/"Seconds"]}, QuantityVariable[x, "Length"][ QuantityVariable[t, "Time"]], QuantityVariable[t, "Time"]] but the equivalent for `NDSolve` does not work, at least with the following syntax: NDSolve[{Derivative[1][QuantityVariable[x, "Length"]][ QuantityVariable[t, "Time"]] == Quantity[5, "Meters"/"Seconds"]}, QuantityVariable[x, "Length"][ QuantityVariable[t, "Time"]], {QuantityVariable[t, "Time"], Quantity[0, "Seconds"], Quantity[10, "Seconds"]}]

Just my guess: Interpolation and InterpolatingPolynomial are not (yet?) compatible with physical units. The documentation for QuantityVariable shows an example of DSolve with units:

DSolve[{Derivative[1][QuantityVariable[x, "Length"]][
    QuantityVariable[t, "Time"]] == 
      Quantity[5, "Meters"/"Seconds"]}, 
 QuantityVariable[x, "Length"][
    QuantityVariable[t, "Time"]], QuantityVariable[t, "Time"]]

but the equivalent for NDSolve does not work, at least with the following syntax:

NDSolve[{Derivative[1][QuantityVariable[x, "Length"]][
    QuantityVariable[t, "Time"]] == 
      Quantity[5, "Meters"/"Seconds"]}, 
 QuantityVariable[x, "Length"][
    QuantityVariable[t, "Time"]], {QuantityVariable[t, "Time"], 
  Quantity[0, "Seconds"], Quantity[10, "Seconds"]}]

POSTED BY: Gianluca Gorni

Reply to this discussion

Reply Preview

Attachments

Remove Add a file to this post

Follow this discussion

or Discard

Feedback