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Jan 30, 2015
03:42 PM

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Jan 30, 2015
03:42 PM

3D Scatter Plot with Natural Log Element MathCAD 14

In MathCAD 14, I am having trouble making a 3D scatter plot when the matrix-function contains an element that is a natural log function. The same matrix-function plots OK If I substitute and different function for the natural log function. I have included an example file; why does the p.2xyz function plot OK and p.1xyz not plot at all?

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Jan 30, 2015
04:57 PM

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Jan 30, 2015
04:57 PM

Unlike a 2D-plot a 3D plot will not respect and use your range t. So you used the 3D quickplot and it defaults to a range from -5 to 5. Give it a try, change your t-range and watch your second plot - nothing will happen.

The negative values in the range [-5; 5] throw a complex result, 0 makes the log function fail. Unlike a 2D plot a 3D plot fails if just one result is complex or NaN or the like.

To make your plot work you have to edit the quickplot range accordingly:

It may be more convenient to use the CreateSpace() function at the price of having to get rid of the units (which you should do in a 3D-plot anyway):

6 REPLIES 6

Jan 30, 2015
03:46 PM

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Jan 30, 2015
03:46 PM

correction: "substitute a dirfferent" not "substitute and dirfferent"

Jan 30, 2015
05:01 PM

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Jan 30, 2015
05:01 PM

Erroll Brady wrote:

correction: "substitute a dirfferent" not "substitute and dirfferent"

Even better "substitute a different", I guess.

BTW, as long as nobody has replied to a post of yours, you can still edit it. If its the initial post you find the option to do so in the outer right column, otherwise at the end of the posting.

Feb 02, 2015
12:28 PM

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Feb 02, 2015
12:28 PM

Yes. I suffer from doofus-finger.

Thanks.

Feb 02, 2015
12:41 PM

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Feb 02, 2015
12:41 PM

Erroll Brady wrote:

Yes. I suffer from doofus-finger.

Thanks.

I can perfectly understand that as I have a similar problem 😉

Hope the answer below helped anyway.

Jan 30, 2015
04:57 PM

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Jan 30, 2015
04:57 PM

Unlike a 2D-plot a 3D plot will not respect and use your range t. So you used the 3D quickplot and it defaults to a range from -5 to 5. Give it a try, change your t-range and watch your second plot - nothing will happen.

The negative values in the range [-5; 5] throw a complex result, 0 makes the log function fail. Unlike a 2D plot a 3D plot fails if just one result is complex or NaN or the like.

To make your plot work you have to edit the quickplot range accordingly:

It may be more convenient to use the CreateSpace() function at the price of having to get rid of the units (which you should do in a 3D-plot anyway):

Feb 02, 2015
12:42 PM

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Feb 02, 2015
12:42 PM

Thank you,

That did the trick.

Erroll