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

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Bhagat
Bhagat 2011-2-28
[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........

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采纳的回答

Walter Roberson
Walter Roberson 2011-2-28
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.

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Matt Fig
Matt Fig 2011-2-28
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.
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Matt Fig
Matt Fig 2011-2-28
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.

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