# Plotting a 3D graph, incorrect solution.

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Pulkit Sharma on 1 Mar 2018
Edited: Pulkit Sharma on 2 Mar 2018
clc
clear
p00 = 553.6;
p10 = 23.56;
p01 = -24.72;
p20 = 212.1;
p11 = -301.9;
p02 = 186.9;
p30 = -2.76;
p21 = -1.261;
p12 = -7.603;
p03 = 11.23;
p40 = -54.55;
p31 = 30.5;
p22 = 10.44;
p13 = 36.48;
p04 = -48.45;
m=1;
n=1;
for x=-100:1:100
n=1;
for y=-100:1:100
Z(m,n)=p00+p10*x+p01*y+p20*x^2+p11*x*y+p02*y^2+p30*x^3+p21*x^2*y+p12*x*y^2+p03*x^3+p40*x^4+p31*y^3*y+p22*y^2*x^2+p13*x*y^3+p04*y^4
n=n+1;
end
m=m+1;
end
surf(x,y,Z)
title('3D PLOT'),xlabel('\bfX'),ylabel('\bfY'),zlabel('\bfZ')
This is the code that gets the Z array, which is to be plotted. Rewriting this in vectorised form, I have
clc
clear
x=-100:1:100;
y=-100:1:100;
p00 = 553.6;
p10 = 23.56;
p01 = -24.72;
p20 = 212.1;
p11 = -301.9;
p02 = 186.9;
p30 = -2.76;
p21 = -1.261;
p12 = -7.603;
p03 = 11.23;
p40 = -54.55;
p31 = 30.5;
p22 = 10.44;
p13 = 36.48;
p04 = -48.45;
[X Y]=meshgrid(x,y);
Z=p00+p10*X+p01*Y+p20*X^2+p11*X*Y+p02*Y^2+p30*X^3+p21*X^2*Y+p12*X*Y^2+p03*Y^3+p40*X^4+p31*X^3*Y+p22*X^2*Y^2+p13*X*Y^3+p04*Y^4
surf(X,Y,Z)
title('3D PLOT'),xlabel('\bfX'),ylabel('\bfY'),zlabel('\bfZ')
Why am I getting separate solutions for both, when the solution should be the one that I am getting from the second one. (solution here is the values in Z). Any help would be most appreciated.
Solved, I was not putting the dots before the product and power operators.

Seyedali Mirjalili on 2 Mar 2018
The problem is that after exiting the for loops, x and y are both equal to 100. So, they are scalars and cannot be used in surf. The function surf requires 2D matrices.
Pulkit Sharma on 2 Mar 2018
So, I do I use the surf option to plot that function?