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01-15-2013
07:25 AM

01-15-2013
07:25 AM

Hi,

Attached is a mathcad worksheet - when you scroll down you will see a set of questions to my problem and a plot of the function that I have produced to try and plot the curve that I want. The curve I wish to plot should look something like the sketch attached (see curve_sketch file) Plot points on the sketch refer to the nomenclature in the mathcad file.

Can you please read the questions in matchad file and advise how best to plot the individual functions of the curve?

Many thanks

Omar

Solved! Go to Solution.

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01-15-2013
09:49 AM

01-15-2013
09:49 AM

If you normalise the x parameter for each stage

here mod(x)-Xeb then the start point needs a constant added, equal to the result from the previous stage at Xeb in this case already calculated as Rub.

If you calculate everything as mod(x) here, saving the result as a local variable (r).

Then the final answer can be returned as

Regards

Andy

10 REPLIES 10

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01-15-2013
07:38 AM

01-15-2013
07:38 AM

Re: Help please - plotting curve as a series of functions

I'll take a look when I have some more time.

In the meantime maybe the following link will be of help concerning plotting of piecewise defined functions.

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01-15-2013
08:56 AM

01-15-2013
08:56 AM

Re: Help please - plotting curve as a series of functions

Thanks Werner

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01-15-2013
09:48 AM

01-15-2013
09:48 AM

Re: Help please - plotting curve as a series of functions

See if this helps.

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01-15-2013
10:54 AM

01-15-2013
10:54 AM

Re: Help please - plotting curve as a series of functions

Hi Fred, thanks for your approach it solves plotting the curve correctly. If you read my response below to Andy I upload a further file - there is a scaler issue in my differential equation that I need to fix to solve my problem.

Many thanks

Omar

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01-15-2013
09:49 AM

01-15-2013
09:49 AM

If you normalise the x parameter for each stage

here mod(x)-Xeb then the start point needs a constant added, equal to the result from the previous stage at Xeb in this case already calculated as Rub.

If you calculate everything as mod(x) here, saving the result as a local variable (r).

Then the final answer can be returned as

Regards

Andy

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01-15-2013
10:25 AM

01-15-2013
10:25 AM

Re: Help please - plotting curve as a series of functions

Hi Andy,

That's great you've solved the problem for plotting the curve. However I encounter another problem when I apply the curve to my differential equation which I solve using the Runge Kutta method. I have attached an updated version of the mathcad file - if you can please take a look and let me know how I resolve the scaler issue so it solves the differential equation.

Many thanks

Omar

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01-15-2013
11:27 AM

01-15-2013
11:27 AM

Re: Help please - plotting curve as a series of functions

Hi Omar,

2 problems:

1

You have Rmu * (...

It should be just Rmu(...

& 2

Rmu is set for parameter in m and returning value as N

All the other functions only return number results (no units)

If you remove the units from Rmu (as above) you get an answer.

However, I have tried adding units to the other equations & still get errors!!

So possible that the answer given may not be correct.

Regards

Andy

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01-15-2013
11:36 AM

01-15-2013
11:36 AM

Re: Help please - plotting curve as a series of functions

Hi Andy

I have tried removing Rmu units as shown however don't get an answer. Can you please provide your worksheet with answer?

Thanks

Omar

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01-15-2013
11:50 AM

01-15-2013
11:50 AM

Re: Help please - plotting curve as a series of functions

Hi Omar,

Don't think that I diod anything else to the sheet, so here it is.

If you spot a difference, please let me know

Regards

Andy

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01-15-2013
12:34 PM

01-15-2013
12:34 PM

Re: Help please - plotting curve as a series of functions

Hi Andy

That works and gives me the sollution i'm looking for. Thank you for your help with this.

Kind regards

Omar