Extracting values from a graph.

[GraceSturgess]

I am new to Mathcad and I want to be able to look up the values of points on a curve. Looking at the help it appears that "traces" should do that, but I cannot get it to work.
Help!
Grace

[TomGutman]

Usually you don't do that. You just get the values directly from the data generatig the graph.
__________________
� � � � Tom Gutman

[PhilipOakley]

If you are using Pictures, then there is a way of
getting the values under the cursor to be returned
to a MathCAD variable.

However for a 2d graph you can't return the
answers to a variable.

In V11, if you right click and select Trace... a
dialog pops up. You then click again into the
graph at the relevant point and its X & Y values
are displayed for you to read. You can use lect
and right arrow keys to move along the graph

In V14, the dialog also gives buttons to copy the
X, Y1 or Y2 values to the clipboard for pasting
back in to the sheet or a report etc. There is a
tick box to enable/disable the left/right key
tracking.

It sounds like a useful concept for the current
feature suggestion request 😉

Philip Oakley

[StuartBruff]

On 11/3/2009 6:50:28 PM, philipoakley wrote:
== It sounds like a useful concept for the current feature suggestion request 😉

Already on it, Philip 🙂

Stuart

http://collab.mathsoft.com/read?130017,12

10. Allow greater interaction with 2D plots (or even 3D plots) to return specific values such as Trace values, slope at a given point, nearest min/max/zero, area under plot, intersection.

[ptc-1368288]

>10. Allow greater interaction with 2D plots (or even 3D plots) to return specific values such as Trace values, slope at a given point, nearest min/max/zero, area under plot, intersection.<<br> _______________________________

Why not add more plot types/functions ... :
normal, tangent, osculating circle, curvature, evolute, involute, auto spline fit the data set, click there and get the data table of all sort, animate, return Cartesian/parametric, filter/smooth data ... sky is the limit.

jmG

[GraceSturgess]

Right clicking I see now will give the values I entered, but none in between. What I wanted was to define a graph with a set of points, fit to a curve, then look at intermediate point.
Thanks
Grace

[TomGutman]

Just evaluate the fit -- the graph is just eye candy, helpful to verify that you have a reasonable fit, but not a source of data.
__________________
� � � � Tom Gutman

[ptc-1368288]

>What I wanted was to define a graph with a set of points, fit to a curve, then look at intermediate point.<<br> ________________________

Fitting a data set is a good way to learn about Mathcad. Attach your work sheet "Save as 11". Many collabs like that kind of project, with an immense library of models. One way or another, you will have either a model function or an interpolating function (spline, polynomial, rational ... ), all analytical. Splines are analytical to the 2nd order derivative.

jmG

[ptc-1368288]

On 11/3/2009 6:20:56 PM, gracehjs wrote:
>I am new to Mathcad and I want
>to be able to look up the
>values of points on a curve.
>Looking at the help it appears
>that "traces" should do that,
>but I cannot get it to work.
>Help!
>Grace
______________________________

That is a very crude way of doing. The other approach is getting the InverseFunction, that's what the tracking toll uses. If you discretize fine enough, you can interpolate. The work sheet "Save as " 11 or lower will surely help you as it will be replied.

jmG

[AlvaroDíaz]

Even you can't extract information from the plot, you can ensure that the information showed in the plot is that what you have at hand.

Regards. Alvaro.