VSQ: I need your help to plot a 4D function (the 4th dimension is the colour)

The function I have to plot is:

RamBoxCox=0.0688 - 0.0748 * E + 0.000079 * PRR + 0.000209 * v - 0.00882 * S - 0.00231 * E*PRR + 0.000099 * PRR*S - 0.000001 * PRR*v*S

I've tried to plot it in this way:

clc
close all
clear all
syms PRR v E S

assume (0.1 < E < 0.1)
assume(1 < S < 4)
assume(20 < PRR < 70)
assume(25 < v < 100)
RamBoxCox=0.0688 - 0.0748 * E + 0.000079 * PRR + 0.000209 * v - 000882 * S - 0.00231 * E*PRR + 0.000099 * PRR*S - 0.000001 * PRR*v*S

%%Plot
% 
cs=25;
cm=jet(cs*5);
ezsurf(E,v,RamBoxCox,'color',cm(S*cs,:))

In this way, the error is that the symbolic variable doesn't implementate the <=,< ecc...

Could you help me?

[Jan]

Please format your code properly and use meaningful tags. Thanks.

The brute clearing header "clc; close all; clear all" wastes a lot of time, usually deletes existing results, but has advantages only in case of massive programming errors, which should be caught by smarter methods.

Answer 1

[Walter Roberson]

Which MATLAB version are you using? I think the ability to use chains of relationships like

assume (1 < S < 4)

must be quite new. Try

assume( 1 < S & S < 4)

Note: you assume() that E is greater than 0.1 and less than 0.1, which is the empty set.