Directional Derivative - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Software Libraries (/forum-10.html) +--- Forum: HP Prime Software Library (/forum-15.html) +--- Thread: Directional Derivative (/thread-3853.html) Directional Derivative - salvomic - 05-15-2015 08:26 PM hi all, my proposal for a function to calculate directional derivative ( $$\bigtriangledown f \cdot \overrightarrow{v}$$ ). It's a CAS program. Use: derivdir(f,v), where f is a function and v a vector. I would like to thank Han for his hints in making this program. Enjoy! Salvo Code:  #cas // Directional derivative: dot(grad(f0), normalize(v)) derivdir(f,v):= BEGIN local g:=grad(f,[x,y,z]); // gradient local w:=normalize(v); // versor m:=dot(g,w); // dot product return m; END; #end RE: Directional Derivative - Tonig00 - 05-11-2019 11:21 AM Nice program. It works. Curious that DOT product should be written in lowercase letters. Also "local" seems to be necessary in lowercase. Thanks