
Re: Explicit function definition
MikeArmstrong Feb 12, 2012 11:40 PM (in response to ptc4457992)Yes I believe it is possible, but I'm not sure exactly what your after.
Could you provide an example and post the worksheet?
Mike

Re: Explicit function definition
ptc4457992 Feb 19, 2012 1:46 PM (in response to MikeArmstrong)Hello!
Thank you for your answer. I don’t have a worksheet yet, but here is what I want to do (I simplified the problem a bit). I have the following (x y) data set where y represents the value of the derivate function at point x:
X Y
0 0
0.2 0.1987
0.4 0.3894
0.6 0.5646
0.8 0.7174
1 0.8415
1.2 0.932
1.4 0.9854
1.5708 1
What I want is to get the value of the function, by numerical integration, at these x points. I don’t need any curve fitting, interpolation function or any other kind of approximation. Could you give me some hints on how to solve this problem with Mathcad?


Re: Explicit function definition
VladimirN. Feb 12, 2012 11:42 PM (in response to ptc4457992)Hello!
Provide a screenshot of what you want.

Re: Explicit function definition
ptc4457992 Feb 19, 2012 1:46 PM (in response to VladimirN.)Hello!
Thank you for your answer. I don’t have a worksheet yet, but here is what I want to do (I simplified the problem a bit). I have the following (x y) data set where y represents the value of the derivate function at point x:
X Y
0 0
0.2 0.1987
0.4 0.3894
0.6 0.5646
0.8 0.7174
1 0.8415
1.2 0.932
1.4 0.9854
1.5708 1
What I want is to get the value of the function, by numerical integration, at these x points. I don’t need any curve fitting, interpolation function or any other kind of approximation. Could you give me some hints on how to solve this problem with Mathcad?


Re: Explicit function definition
FredKohlhepp Feb 13, 2012 3:46 AM (in response to ptc4457992)Given an x,y data set there are several ways to proceed; the choice depends on the data and what you want to do. With a dense and complete data set you can use numerical integration techniques. You can curve fit the datafind a function that approximates the data closely, and use the builtin integration schemes for manipulation.

Re: Explicit function definition
ptc4457992 Feb 19, 2012 1:45 PM (in response to FredKohlhepp)Hello!
Thank you for your answer. I don’t have a worksheet yet, but here is what I want to do (I simplified the problem a bit). I have the following (x y) data set where y represents the value of the derivate function at point x:
X Y
0 0
0.2 0.1987
0.4 0.3894
0.6 0.5646
0.8 0.7174
1 0.8415
1.2 0.932
1.4 0.9854
1.5708 1
What I want is to get the value of the function, by numerical integration, at these x points. I don’t need any curve fitting, interpolation function or any other kind of approximation. Could you give me some hints on how to solve this problem with Mathcad?


Re: Explicit function definition
A.Non Feb 13, 2012 6:54 AM (in response to ptc4457992)You need to create an interpolating function. The most general solution is a cubic spline, but it's not always appropriate. Without seeing the data it's hard to say much more.

Re: Explicit function definition
ptc4457992 Feb 19, 2012 1:46 PM (in response to A.Non)Hello!
Thank you for your answer. I don’t have a worksheet yet, but here is what I want to do (I simplified the problem a bit). I have the following (x y) data set where y represents the value of the derivate function at point x:
X Y
0 0
0.2 0.1987
0.4 0.3894
0.6 0.5646
0.8 0.7174
1 0.8415
1.2 0.932
1.4 0.9854
1.5708 1
What I want is to get the value of the function, by numerical integration, at these x points. I don’t need any curve fitting, interpolation function or any other kind of approximation. Could you give me some hints on how to solve this problem with Mathcad?

Re: Explicit function definition
A.Non Feb 19, 2012 2:10 PM (in response to ptc4457992)We don't need the same reply four times. It's just as easy to read one reply four times as it is to read four replies
I don’t need any curve fitting, interpolation function or any other kind of approximation.
All numerical integration is approximate. The attached is a very general, and usually accurate, approach.

Integral.xmcdz.zip 7.7 K


