Data Analysis Routines¶
These modules provide basic data analysis or data fitting functionality.
linefit¶
Fit a line to a data set with optional weights.
Returns the parameters of the model, bo, b1: Y = b0 + b1* X
- author:
Nadia Dencheva
- version:
‘1.0 (2007-02-20)’
- stsci.tools.linefit.linefit(x, y, weights=None)¶
- Parameters:
- y: 1D numpy array
The data to be fitted
- x: 1D numpy array
The x values of the y array. x and y must have the same shape.
- weights: 1D numpy array, must have the same shape as x and y
weight values
Examples
>>> import numpy as N >>> from numpy import around >>> x = np.array([-5, -4 ,-3 ,-2 ,-1, 0, 1, 2, 3, 4, 5]) >>> y = np.array([1, 5, 4, 7, 10, 8, 9, 13, 14, 13, 18]) >>> around(linefit(x,y), decimals=5) array([9.27273, 1.43636]) >>> x = np.array([1.3,1.3,2.0,2.0,2.7,3.3,3.3,3.7,3.7,4.,4.,4.,4.7,4.7,5.,5.3,5.3,5.3,5.7,6.,6.,6.3,6.7]) >>> y = np.array([2.3,1.8,2.8,1.5,2.2,3.8,1.8,3.7,1.7,2.8,2.8,2.2,3.2,1.9,1.8,3.5,2.8,2.1,3.4,3.2,3.,3.,5.9]) >>> around(linefit(x,y), decimals=5) array([1.42564, 0.31579])
xyinterp¶
- Module:
xyinterp.py
Interpolates y based on the given xval.
x and y are a pair of independent/dependent variable arrays that must be the same length. The x array must also be sorted. xval is a user-specified value. This routine looks up xval in the x array and uses that information to properly interpolate the value in the y array.
- author:
Vicki Laidler
- version:
‘0.1 (2006-07-06)’
- stsci.tools.xyinterp.xyinterp(x, y, xval)¶
- Purpose:
Interpolates y based on the given xval.
x and y are a pair of independent/dependent variable arrays that must be the same length. The x array must also be sorted. xval is a user-specified value. This routine looks up xval in the x array and uses that information to properly interpolate the value in the y array.
- Parameters:
- x: 1D numpy array
independent variable array: MUST BE SORTED
- y: 1D numpy array
dependent variable array
- xval: float
the x value at which you want to know the value of y
- Returns:
- y: float
the value of y corresponding to xval
- Raises:
- ValueError:
If arrays are unequal length; or x array is unsorted; or if xval falls outside the bounds of x (extrapolation is unsupported
- version:
0.1 last modified 2006-07-06 ..
See also
Notes
Use the searchsorted method on the X array to determine the bin in which xval falls; then use that information to compute the corresponding y value.