Matlab transpositions from formula

Having some dramas converting equations to matlab. The code runs but my answers seem wildly out...

Part A uses the formula v=(T^3/2)/a*T+b which i believe translates to V = (T.^3/2)./A.*T+B; in matlab. I think this is right.

Part b uses the formula 1/v=a*(T^-1/2)+b*T^-3/2 which I thought to be in matlab as...

Vtemp = (A2.*TCK.^-1/2)+(B2.*TCK.^-3/2);

V2=1./Vtemp;

Part C runs a formula f(c,t)=(T^3/2)/c(1)*T+c(2) which i am mostly sure is right but not 100%.

clear; close all; clc

%% problem 4

TC = [-20 0  20 40 70 100 200 300 400 500]';
vi = [1.63 1.71 1.82 1.87 2.03 2.17 2.53 2.98 3.32 3.64]';
TCK = TC + 273.15;

%% part a

p = polyfit(1./TCK,vi,1);
B = p(1);
A = p(2);

V = (TCK.^3/2)./A.*TCK+B;
Tspan = linspace(-20,520,10)';
plot(Tspan,V,'bo',Tspan,V,'r-');
grid on
xlabel('Temp')
ylabel('Viscocity')
title('viscosity polyfit part a')

 %% part b
 
p2 = polyfit(1./TCK,vi,1);
B2 = p2(1);
A2 = p2(2);

Vtemp = (A2.*TCK.^-1/2)+(B2.*TCK.^-3/2);
V2=1./Vtemp;
Tspan = linspace(-20,520,10)';
figure; plot(Tspan,V2,'bo',Tspan,V2,'r-');
grid on
xlabel('Temp')
ylabel('Viscocity')
title('viscosity polyfit part b')
 
%% part c

f = @(c,T) T.^3/2./c(1).*T+c(2);
c0 = [1;1];
c = nlinfit(TCK,vi,f,c0);
V3 = f(c,Tspan);
figure; plot(Tspan,V3,'bo',Tspan,V3,'r-');
grid on
xlabel('Temp')
ylabel('Viscocity')
title('viscosity nlinfit part C')

%% part d

% title('viscosity - polyfit-2 method')
% 
% fprintf('    A          B        method\n')
% fprintf(['-------------------------------','\n'])
% fprintf(' %6.4f   %6.4f     %-7s\n',A2,B2,'polyfit-2')

Answer 1

[Paul]

Maybe you really mean to put all those fractional exponents inside parentheses? For example:

Tck = 4;
Tck.^3/2   % or

ans = 32

Tck.^(3/2) % equivalent to

ans = 8

Tck.^1.5

ans = 8