Re: Sine function won't resolve correct treadline

Darren Marshall wrote:
> I came across a little problem. I have a data list, the time of sunrise on the 
> first of the month for twelve months. A perfect sine, right? Well, after 
> plotting the data on Graph and asking it to make a sinusodial treadline, it 
> came up with something weird... Here's the data. See if you can replicate it.

Graph uses an initial guess to search for the nearest optimum for the 
constants that gives the best trendline. The problem is that some 
models, like this one, have more than one local optimum, and Graph will 
usually find the one closest to the initial guess. Therefore you may 
need to change the initial guess, which defaults to 1.

I was not aware the TI-83 could find trendlines, but I can see that it 
only works for some specific functions where it apparently knows what to 
use for the initial guess.

I will consider to do something similar in Graph, and add some special 
functions, like the sinusoidal, and have Graph automatically find an 
initial guess for them. That would probably make it more user friendly.

Best regards
Ivan Johansen

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Adding two point series

I have a series of point series that can't be converted to a function using 
trendlines.  

Is there any way of adding one point series with another to get a third series?

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Portable Graph

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Re: Adding two point series

Alfredo Vincenty wrote:
> I have a series of point series that can't be converted to a function using 
> trendlines.  
> 
> Is there any way of adding one point series with another to get a third series?

First you can use Edit|Copy followed by Edit|Paste to make a copy of the 
first point series. When you can edit the second point series, select 
all the points, and use Ctrl+C to copy the points. At last you can edit 
the newly pasted point series and use Ctrl+V to paste the points from 
the second series.

Best regards
Ivan Johansen

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Re: Adding two point series

Ivan Johansen <graph <at> padowan.dk> writes:

> 
> Alfredo Vincenty wrote:
> > I have a series of point series that can't be converted to a function 
using 
> > trendlines.  
> > 
> > Is there any way of adding one point series with another to get a third 
series?
> 
> First you can use Edit|Copy followed by Edit|Paste to make a copy of the 
> first point series. When you can edit the second point series, select 
> all the points, and use Ctrl+C to copy the points. At last you can edit 
> the newly pasted point series and use Ctrl+V to paste the points from 
> the second series.
> 
> Best regards
> Ivan Johansen
> 
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> This SF.net email is sponsored by: Microsoft
> Defy all challenges. Microsoft(R) Visual Studio 2008.
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> 

Hi Ivan,

What I meant was to be able to add series 1 to series 2 to get a new curve.  
Similar to having a curve represented by Function 1 + Function 2.

Thanks

Alfredo

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Re: Portable Graph

Kendrick Feller wrote:
> Have you considered making Graph a portable application? I don't know 
> how hard it is but it could be useful. For example if you wanted to 
> write a report on a school computer that doesn't allow software 
> installation. Or if you are just using a friends computer and don't want 
> to install anything. 

Actually you can just copy the installed Graph.exe to another computer 
and run it. The only problem is that it will store some settings on the 
computer when run. I am looking at the possibility to optionally store 
the settings in a file instead.

> By the way I love your program. It is simply a must 
> have for lab reports. It is much more powerful than the standard graph 
> features included in office suites. Thanks for making it.

I am glad to hear that you like it.

Best regards
Ivan Johansen

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Re: Adding two point series

Alfredo Vincenty wrote:
> What I meant was to be able to add series 1 to series 2 to get a new curve.  
> Similar to having a curve represented by Function 1 + Function 2.

Sorry, I misunderstood you. This is not currently possible, but I think 
it will be when Graph 4.4 is finished.

Until when you can instead copy the point series to a spread sheet, e.g. 
MS Excel, which can add the series. You can then copy the points back 
into Graph.

Best regards
Ivan Johansen

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Differentiation error

If you derive e^x, instead of just getting e^x back, you get e^x*ln(e). I can
see this is the same, but why does it do it?

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Polar graphs

Is it possible to use polar axis (in a circle like this:
http://upload.wikimedia.org/wikipedia/commons/a/a3/Circle_r%3D1.PNG)? If not,
will they be in future versions.

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Re: Polar graphs

Jordan Watts wrote:
> Is it possible to use polar axis (in a circle like this:
> http://upload.wikimedia.org/wikipedia/commons/a/a3/Circle_r%3D1.PNG)? If not,
> will they be in future versions.

I have it on my todo list, but I don't know when I will have the time to 
implement it.

Best regards
Ivan Johansen

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