Unrecognized function or variable 'CP'. Error in solution (line 66) text(c+.5,​f(c),["("+​string(c)+​","+string​(f(c))+") "+CP ])

%Use symbolic processing with the variable x
syms x

%Enconde the function f(x)
num = (1-x^2)
denom = (1+x^2)
f(x) = num/denom
eqn = num/denom==0
cc1= solve(eqn)
%Set the distance to the left/right of the critical point
h=0.01

%Find the first derivative of the function
fp(x) = diff(f(x))

%Solve for the roots of fp
root1 = solve(fp)

%Consider the first critical point only
c=root1(1)

%Determine if the function is "Increasing" or "Decreasing" at the right of the critical point
if (fp(c+h)>0)
    IoDR = "increasing"
elseif (fp(c+h)<0)
    IoDR = "decreasing"
end

%Determine if the function is "Increasing" or "Decreasing" at the right of the critical point
if (fp(c-h)>0)
    IoDL =  "decreasing"
elseif (fp(c-h)<0)
    IoDL ="increasing"
end

%Use first derivative Test to Determine if the critical point is a "Maximum" point or "Minimum" point.
if IoDL=="Increasing" & IoDR =="Decreasing"
    CP= "Maximum"
elseif IoDL=="Decreasing" & IoDR =="Increasing"
    CP= "Minimum"
end

%Find the second derivative of the function
fpp(x)= diff(f,2);
eqn1 = fpp==0
%Find the points of inflection of the function by equating the second derivative of the function to zero.
cc = solve(eqn1)

%Apply Second Derivative Test to check whether the critical point is a "Maximum" point, a "Minimum" point or "Point of Inflection".
if fpp(c) >0
    CP2 = "Maximum"
elseif fpp(c)<0
    CP2 = "Minimum"
else
    CP2 = "Point of Inflection"
end


%GRAPH THE FUNCTION
clf();
g1= ezplot(f);
hold on
grid on
plot(c,f(c), 'r*')
title("Curve Tracing")
text(c+.5,f(c),["("+string(c)+","+string(f(c))+")   "+CP  ])

I'm still new to Matlab, Please assist me in resolving this issue at line 66. Thank you very lot.

Unrecognized function or variable 'CP'. Error in solution (line 66) text(c+.5,f(c),["("+string(c)+","+string(f(c))+") "+CP ])

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[Walter Roberson]

You have

if IoDL=="Increasing" & IoDR =="Decreasing"
    CP= "Maximum"
elseif IoDL=="Decreasing" & IoDR =="Increasing"
    CP= "Minimum"
end

but if both of them are increasing or both of them are decreasing then you do not assign anything to CP.

[MJ]

Thank you, however I already answered this question, and the incorrect code is only a capital letter.

[Walter Roberson]

Well that is difficult to verify now that the code is removed. From what I recall of the code, the issue I pointed out is also a problem.