Error correction...inner matrix dimensions must be same??? how to correct ?

[EDIT: 20110610 00:25 CDT - reformat - WDR]

I wrote the following code:

------------------------

w=10:2:30;
a=4*((9*w)-7);
b=(-2)*((18*w)-16)*(w+1);
c=3*((w+1)^2)*((3*w)-1);
d=(-3)*((1+w)^3);
f = roots([a,b,c,d]);
f=f(f<1);
ptr=2./(1+w);
u=(1+w)./2;
l=(u*(1-ptr*f)^3)./3;
plot(w,l);

--------------------------

It shows the following error:

??? Error using ==> mtimes
Inner matrix dimensions must agree.

Error in ==> cubic at 3
b=(-2)*((18*w)-16)*(w+1);

======================

I am not able to correct it .Please help........

Answer 1

[Walter Roberson]

There are significant difficulties with the code that are being explored in the thread about cubic roots. Please do not spread the discussion over two threads.

[Bhagat]

Sry,was getting impatient

Answer 2

[Matt Fig]

You must put a dot before any *, / or ^ used when you want element-by-element operations on arrays of the same size. Note that if the arrays are not of the same size (or scalar), all bets are off.

A.*B 
A./B
A.^B

Also, look at your other post (about cubic roots), I showed you this there too.

[Bhagat]

w=10:2:30;

a=4*((9*w)-7);

b=(-2)*((18*w)-16).*(w+1);

c=3*((w+1).^2).*((3*w)-1);

d=(-3)*((1+w).^3);

f = roots([a,b,c,d]);

f=f(f<1);

ptr=2./(1+w);

u=(1+w)./2;

l=(u.*(1-(ptr.*f).^3))./3;

plot(w,l);

============================

In the above code following error is coming:

??? Error using ==> times

Matrix dimensions must agree.

Error in ==> cubic at 10

l=(u.*(1-(ptr.*f).^3))./3;

==================================

How and which matrix dimensions don't agree here ???

[Sean de Wolski]

{u, pte, f} must all be the same size or scalar

[Matt Fig]

Did you look at the other post? You keep posting the same erroneous code over and over, but did you try what I wrote in the other post???? I ran it and got no errors.