I have solved a system of differential equations, whereby some of the variables are presenting integration drift in the results.
I have attached a spreadsheet with the results of one of the variables (theta) note that the time component was exluded to keep the file small. The time increments are 0.0001seconds with t starting at 0.
The plot of the results is presented below.
The inital conditions of the problem has theta = 0.1, which is correct when reviewing the data in the spreadsheet.
I have used the code below to process the data, however upon processing the data the inital condition is no longer true as the value is no longer 1. Note that the code does not present the data being read from the excel file as it already exists in a variable (theta).
Could someone please give me some advice on how one could accurately process the data?
[b a] = butter(4,Fc,'high');