The only needed input for savetxt is the output filename and the arrays it will output. Everything else is optional.
The first argument 'MotionDataOut.txt' is the output file name
The second option np.c_[x,y]. Because we are trying to write not one array but two in the file we need to package the two arrays into one. To do that we use the function c_. If we only needed to print one array we do not need to use .c_ we could just write the array for option. For example: np.savetxt('MotionDataOut.txt',x)
The third option used here is fmt='%1.1f' This option determines how the elements in the file are going to be displayed. The value of fmt here is a string equal to %5.1f. The letter f is for float. The number 8.1 The .1 part displays one decimal digit to the write of the decimal point. The 8. part is the minimum width. 8 in this case is more than any of the digits in each column. This will ensure that columns have the same widths and that the decimal points are aligned.