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ebrady-21-Visitor
1-Visitor
Jan 30, 2015 8:42 PM UTC
Solved

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?

Werner_E
Werner_EAnswer
25-Diamond I
Jan 30, 2015 9:57 PM UTC

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:

1.png

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):

2.png

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6 replies

ebrady-21-VisitorAuthor
1-Visitor
Jan 30, 2015 8:46 PM UTC

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

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Werner_E
Werner_E25-Diamond I
25-Diamond I
Jan 30, 2015 10:01 PM UTC

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.

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ebrady-21-VisitorAuthor
1-Visitor
Feb 2, 2015 5:28 PM UTC

Yes. I suffer from doofus-finger.

Thanks.

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Werner_E
Werner_E25-Diamond IAnswer
25-Diamond I
Jan 30, 2015 9:57 PM UTC

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:

1.png

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):

2.png

Translate
ebrady-21-VisitorAuthor
1-Visitor
Feb 2, 2015 5:42 PM UTC

Thank you,

That did the trick.

Erroll

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