image thumbnail

DGradient

version 1.0.0.0 (12.5 KB) by Jan
Gradient of arrays as fast C-Mex

2.6K Downloads

Updated 02 Jan 2011

View License

Gradient along a specified dimension

Y = DGradient(X, Dim, Spacing, Method)
INPUT:
X: Real DOUBLE array, any number of dimensions.
Spacing: Scalar or vector of the length SIZE(X, Dim).
Dim: Dimension to operate on.
Optional, default: 1st non-singelton dimension.
Method: String, order of the applied method for unevenly spaced X:
'1stOrder', faster centered differences as in Matlab's GRADIENT.
'2ndOrder', 2nd order accurate centered differences.
On the edges forward and backward difference are used.
Optional, default: '1stOrder'.

OUTPUT:
Y: Gradient of X, same size as X.

There are a lot of other derivation tools in the FEX. This function is faster (e.g. 25% faster than dqdt and 10 to 16 times faster than Matlab's GRADIENT), works with multi-dim arrays, on a specific dimension only, and can use a 2nd order method for unevenly spaced data.
For vectors or evenly spaced data no temporary memory is needed. Otherwise 1 or 3 temporary vectors of SIZE(X, Dim) are used for the 1st and 2nd order methods.

The C-Mex file must be compiled at first. Pre-compiled files for Win32 can be downloaded at: http://www.n-simon.de/mex
Run the unit-test function uTest_DGradient to check the integrity and measure speed.

Tested: Matlab 6.5, 7.7, 7.8, WinXP, 32bit
Compiler: LCC2.4/3.8, BCC5.5, OWC1.8, MSVC2008
Assumed Compatibility: higher Matlab versions, Mac, Linux, 64bit

Thanks to Robert A. Canfield (central_diff, #12) and Darren Rowland (diffxy, #29312).

Cite As

Jan (2021). DGradient (https://www.mathworks.com/matlabcentral/fileexchange/29887-dgradient), MATLAB Central File Exchange. Retrieved .

MATLAB Release Compatibility
Created with R2009a
Compatible with any release
Platform Compatibility
Windows macOS Linux
Categories

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!