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6983 Views 22 Replies Latest reply: Mar 12, 2011 5:32 AM by PhilipOakley RSS
IanRiensche Copper 7 posts since
Jan 12, 2011
Currently Being Moderated

Jan 12, 2011 2:27 PM

Polar Coordinates

Does anyone know how to display complex calculated results in polar coordinates?  I realize one can enter polar coordinates in complex calculations using Euler's formula, but MathCAD always returns the result in Cartesian coordinates.  This is particularly annoying, especially if one is trying to compare the calculated values to the input values.  If there isn't a way to do this, then I think it should be added as a feature to MathCAD.  It's hard to imagine a software package as powerful (and expensive) as MathCAD not offering polar coordinates.  We pay a fee annually to stay current with MathCAD, and I submitted this as a suggestion more than a year ago, but still haven't seen it.  The entire power industry is a sector of the engineering industry that would benefit from this because we deal with polar coordinates all the time.

  • ValeryOchkov Platinum 6,121 posts since
    Sep 26, 2008
    Currently Being Moderated
    Jan 13, 2011 10:24 AM (in response to IanRiensche)
    Re: Polar Coordinates

    It is built-in format in Mathcad Prime.

    In Mathcad ** we can use user tool:

    http://twt.mpei.ac.ru/ochkov/Sovet_MC/169/169.gif 

  • MikeArmstrong Diamond 4,457 posts since
    Dec 3, 2008
    Currently Being Moderated
    Jan 13, 2011 12:27 PM (in response to IanRiensche)
    Re: Polar Coordinates
    The entire power industry is a sector of the engineering industry that would benefit from this because we deal with polar coordinates all the time.

    That is a big statement saying the entire industry would benefit.

    because we deal with polar coordinates all the time.

     

    Sorry to be argumentative, but I actually use Cartesian, but I do agree that Mathcad should include a conversion.

     

    Mike

      • A.Non Diamond 10,327 posts since
        May 11, 2010
        Currently Being Moderated
        Jan 14, 2011 7:11 AM (in response to IanRiensche)
        Re: Polar Coordinates

        but as I pointed out above, one cannot apply a MathCAD function to a calculated result.

        Yes you can (in later Mathcad versions, anyway). See "Help", "Tutorials", "Features in Depth", "Temperature and User Defined Units" for more information.

          • MikeArmstrong Diamond 4,457 posts since
            Dec 3, 2008
            Currently Being Moderated
            Jan 14, 2011 10:20 AM (in response to IanRiensche)
            Re: Polar Coordinates

            Ian Riensche wrote:

             

            Thank you very much for the response. This is the best workaround I've seen to MathCAD's inherint inability display polar coordinates.  Here is a screen shot of the applied function.

            I find thay a very strange statement.

             

            The functions I posted does exactly what you ask for.

             

            Mike

            • A.Non Diamond 10,327 posts since
              May 11, 2010
              Currently Being Moderated
              Jan 14, 2011 11:42 AM (in response to MikeArmstrong)
              Re: Polar Coordinates

              I think the issue is only that your functoins are not defined in such a way they can be used in the units placeholder of a result.

              • MikeArmstrong Diamond 4,457 posts since
                Dec 3, 2008
                Currently Being Moderated
                Jan 14, 2011 12:34 PM (in response to A.Non)
                Re: Polar Coordinates
                I think the issue is only that your functoins are not defined in such a way they can be used in the units placeholder of a result.

                What was the secret behind doing that. I haven't seen that done before or requested on this forum.

                 

                Any other examples?

                 

                Mike

                • A.Non Diamond 10,327 posts since
                  May 11, 2010
                  Currently Being Moderated
                  Jan 14, 2011 12:40 PM (in response to MikeArmstrong)
                  Re: Polar Coordinates

                  The key is that you must have a function pair with the names, for example, "func" and "/func". If you put "func in the units placeholder of a result it applies  "/func" to the results. There are some other examples in "Help", "Tutorials", "Features in Depth", "Temperature and User Defined Units".

          • A.Non Diamond 10,327 posts since
            May 11, 2010
            Currently Being Moderated
            Jan 14, 2011 11:41 AM (in response to IanRiensche)
            Re: Polar Coordinates
            If only I could figure out how to return the angle in degrees instead of radians - any thoughts?

            This is the best I can do.

            • PhilipOakley Silver 2,088 posts since
              Feb 20, 2007
              Currently Being Moderated
              Mar 12, 2011 5:32 AM (in response to A.Non)
              Re: Polar Coordinates

              Richard Jackson wrote:

               

              If only I could figure out how to return the angle in degrees instead of radians - any thoughts?

              This is the best I can do.

               

              The choice of the base unit for Angle, has been another contested item in the Metrologia letters pages over the years, not just the 'is Angle a dimension?' question!

               

              Doing the conversion isn't an issue as long as the unit is explicitly stated (within the units place holder, by the user or mathcad). If Angle were a dimension then Mathcad would positively indicate that its angular results are, by default, in radians, avoiding all these problems.

               

              It is already possible to enter the magnitude & phase values using infix notation, but unfortunately it isn't that easy with the mouse clicks.

               

              It doesn't help that infix isn't listed in the help menu (see postfix instead), however the angle sign is listed as a special symbol, and infix examples are given in the Custom operators quicksheet. All we need is an easy way of getting our chosen function inserted as an infix operator - perhaps a user pallette where we can place our quick access functions!.

               

               

              There is a fundamental problem (for Mathcad) with values which have mixed units, because at the moment mathcad keeps only a single single dimensional factor for both halves of a complex number. This isn't a problem for cartesian representations (e.g. complex voltages = real + imaginary volts), but is a problem with a (magnitude + phase) representations where the magnitude part has volts as its dimensions, while the phase part has Angle as its dimension. Even if you are an adherent of 'Angles are dimesionless', you still have mixed units with magnitude+phase method within the same variable.

               

              It could be an advantage for mathcad to be able to declare a structured variable such that the expected units of the different numeric components could be different, and checked. A complex number is such an implicit structured variable, but with the dimesions applied to the whole structure. In this case the electrical example of magnitude and phase internal representation for say line current, line voltage, and line impedance, with the usual computable relationship V=I.X (where X is the complex impedance). The complex algebra is well defined and understood, which is why we use it, but the other types can be a pain. (e.g. quaternions as a 4-vector, or as bi-complex, or a 2-vector of a scalar plus 3-vector, all of which are equivalent but with different implied calculation rules!).

               

              Most of this is a confusion between (implicit) external representation and internal storage, just like 0.999999999999999999...

               

              philip

               

              Message was edited by: Philip Oakley This replies to the original comment about getting the number in the right units

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