ACCEPTED SOLUTION
Accepted Solutions
John Doe wrote:
Outstanding Werner! Thank you for the effort.
Can you explain what you did in this line?
"cspline" takes two vectors x and y of equal length, does a cubix spline interpolation of the data and returns a matrix. This matrix is fed in the Mathcad function "interp" which takes additionally the two vectors x and y as arguments and at last the x-value we want to calculate the interpolated y-value for.
In our case the abscissa values are the first column of the (now sorted) matrix Cdus, therefore Cdus<0> and the ordinate values are the second column. Cd is the value we are looking for and as I made it a finction (us_interp) its a variable.
You may lookup more informations on "cspline" and "interp" using Mathcads help.
You could have separeted the matrix beforehand by writing C_d:=CDus<0>, etc. but I thought this would not be necessary, as the sorted values would only be of value for cspline.
With the data you provided (5pF) it would not have been necessary to interpolate as this value is exactly one in the data vectors. But if you try one which is not in, you will see how it works. Especially if you compare it to the exact value from method 1. In particular the lookup method will be disappointing as it will only present you with a value in the tables which is the nearest to the demanded for.
