Register to reply

Help with EES (take derivative from table)

by Hobold
Tags: derivative, table
Share this thread:
Aug29-11, 04:37 PM
P: 84
I'm not sure if you're familiar with EES, but just in case I am asking here because I really have no idea what to do, as I've tried everything I could.

Basically, I want to calculate a partial derivative numerically (speed of sound) from a table of values.

I have a program that produces a table of pressures and specif mass and I want to take

[tex] \left( \dfrac{\partial p}{\partial \rho} \right)_s \approx \left(\dfrac{p_{i+1} - p_i}{\rho_{i+1} - \rho_i} \right) [/tex]

I've tried creating procedures, functions and stuff like that but I couldn't do anything. Here's basically what I have done most times:

PROCEDURE Vsound( : vel )




	a := tablevalue('rev';i;'p')
	b := tablevalue('rev';i+1;'p')
	c = tablevalue('rev';i;'rho')
	d = tablevalue('rev';i+1;'rho')

	vel := (b-a)/(d-c)

UNTIL (i=1499)

Basically I have a parametric table called "rev" with columns "p" and "rho" in which I have 1500 values for each.

Then later in the code, after writing stuff to calculate both p and rho, I call that procedure:

CALL Vsound(: vel)

Though it says that there is no value set for rho. I believe that's because rho is calculated within the program (p is pre-set), though I have no idea how to solve this problem.


Thanks in advance
Phys.Org News Partner Engineering news on
California quake points to research advancements in retrofitting older buildings
Greater safety and security at Europe's train stations
Fingerprints for freight items

Register to reply

Related Discussions
Find derivative of floor function using limit definition of derivative? Calculus & Beyond Homework 10
Woman walking around table, find angular speed of table. Introductory Physics Homework 0
Solve derivative by using the definition of the derivative limit Precalculus Mathematics Homework 10
Don't understand material derivative and and advective derivative General Physics 5
Replacing total derivative with partial derivative in Griffiths' book Advanced Physics Homework 3