Need help with average rate of change.

How do I calculate the average rate of change with this as my function:

function y = W(x) if 1 <= x && x <= 28 y = 48+3.64*x+0.6363*x.^2+0.00963*x.^3; end if x>28 && x<=56 y =-1004+65.8*x; end

[sixwwwwww]

What actually you want to do? Because your function consists of polynomial equations in two if conditions. Can you explain briefly?

[Alexander]

I need to create an m-file that will calculate the average rate of change of W over a time interval. We were given the piece wise function:

W(t) = 48+3.64t+0.6363t^2+0.00963t^3 when 1 <= t <= 28 W(t) = -1004+65.8t when 28 < t <= 56

[Lauren]

May I talk to you via e-mail or something?

[Jan]

@Lauren: It is the nature of a public forum to let all readers participate from solutions. Therefore some users do not discuss via emails.

[Alexander]

@Lauren, sure.

Answer 1

[Youssef Khmou]

Alexander, in the range [1 28], the average rate is : 48+3x²+x(2b+3)+h²+a and in the range [28 56] it is : B, with a=3.64, b=0.6363, c=0.00096, and B=65.8.

Verify this using the general formula DY/DX=(F(X+H)-F(X))/H

[Alexander]

I'm new to matlab, how would I type this in to get the m-file?

[Youssef Khmou]

you can visualize your function very fast using the command fplot :

 >>fplot('48+3.64*x+0.6363*x.^2+0.00963*x.^3',[1 28])
 >>figure, 
 >>fplot('-1004+65.8*x',[28 56])

The calculus above are made by theoretically, verify them , and then all you need is replace with boundaries 1 28 56 :

see this page as example : http://home.windstream.net/okrebs/page201.html

[Alexander]

Okay, and if I wanted to find the average change from say t=1 to t=25, how would I do that?

[Youssef Khmou]

then the (h,x) in the formula are x=1, and h=x2-x1=24