Problem E7.3 (LabVIEW)

[khchai]

I've been trying to plot the ellipse with equation on Page 232 of Dr. Robert H. Bishop book but was unsuccessful. Anyone got a suggestion on this? Thanks in advance.

[Ankita A.]

Hi,

You can use the attached vi to plot an ellipse given its equation.

Regards,
Ankita A.
Applications Engineer
National Instruments

[khchai]

Hi,

Thank you for responding to my problem. Actually the problem involve sin and cos function. I attached the problem here. Hope you could help. Thanks in advance.

[Daigon]

I have the same problem.

Briefly, the E7.3 problem is about plotting an ellipse using the equation:

r^2= A^2*B^2/(A^2*sin^2(ф)+B^2cos^2(ф))

where r, A and B are inputs.

Anyone who can help, please?

thank you in advance 

[reikira]

Duplicated Post.

Please see http://forums.ni.com/ni/board/message?board.id=7170&message.id=1314&jump=true

Serena M.

[CMal]

Daigon,

I don't speak Itialian, so I'm posting my answer here instead of in the other thread.

Here's how I would approach the problem:

1. Create an array of values for 'phi' ranging from 0 to 2*pi.  You can use a For loop to do this, and the number of points in the array should depend on how smooth you want your graph to be.
2. With 'A' and 'B' as inputs, and the created 'phi' array as another input, calculate the value of 'R' from the equation provided.  I don't understand how 'R' is supposed to be an input.  Also, remember that you can use the math functions in LabVIEW in either scalars or arrays.  For example, you can multiply an array by a scalar with the 'Multiply' primitive.
3. Create 'X' and 'Y' arrays from the values of 'R' and 'phi', then bundle the 'X' and 'Y' arrays together to plot with and XY Graph.

You should be able to do all of this with loops and simple math in LabVIEW.  You shouldn't need to use a formula node to do this.  Let me know if this helps.

Chris M 

[The cat]

Hi CMal

From your explanation, I am still unable to solve the problem.

Would you be kind enough to help me solve the problem as I am really stuck.

Thank you very much. 

[Mathan]

started a new thread here

[CMal]

The cat,

Can you be more specific on which parts of my explanation you do not understand?  Are you having trouble creating a 1D array of 'phi' values, or is the problem with converting the 'R' values into 'x' and 'y' coordinates?  The more information you can give about what you have tried, the better.

Chris M

[The cat]

Hi CMal

Yes I have trouble creating the 1D array of 'phi' values.

For the equation I have already done it with the fomula node

and plot it on a XY graph using the input A & B but the graph

is not an ellipse, instead it gives me a funny plot.