Thread Subject: Help with compiling a Derivative m-file

Hi to all!

I really need some help with a m-file I'm working on. I know
some math but I'm a total noob with matlab.

I need to write an m-file that does the following operations
to a given function.
-given function = f
-given dot = x
-given spacing = dx

The function that would do all of the operations is named as
fun.

1. The fun function will calculate the derivative of any
given function f in any given dot x.

2. The fun will also calculate the differential of the given
function f in the given dot x, both a estimate and the
accurate value with the given spacing dx.

3. This is tough one. The function fun will calculate the
equation of the tangent for the given function f with the
given dot x.

Here's what I've done so far:

function out = fun(f,x,dx)

out = diff(f,x); %The derivative of the function.

out = (diff(f,x)*dx %The estimated value of the differential.



Problems I have with the m-file:
-How is i possible to get multiple out's from one m-file?
-How can I substitute the x with the given value of the x?

All tips are very welcome. Cheers!

"A " <amutka@welho.com> wrote in message
<fv7a2p$7ap$1@fred.mathworks.com>...
> Hi to all!
>
> I really need some help with a m-file I'm working on. I
know
> some math but I'm a total noob with matlab.
>
> I need to write an m-file that does the following
operations
> to a given function.
> -given function = f
> -given dot = x
> -given spacing = dx
>
> The function that would do all of the operations is named
as
> fun.
>
> 1. The fun function will calculate the derivative of any
> given function f in any given dot x.
>
> 2. The fun will also calculate the differential of the
given
> function f in the given dot x, both a estimate and the
> accurate value with the given spacing dx.
>
> 3. This is tough one. The function fun will calculate the
> equation of the tangent for the given function f with the
> given dot x.
>
> Here's what I've done so far:
>
> function out = fun(f,x,dx)
>
> out = diff(f,x); %The derivative of the function.
>
> out = (diff(f,x)*dx %The estimated value of the
differential.
>
>
>
> Problems I have with the m-file:
> -How is i possible to get multiple out's from one m-file?
> -How can I substitute the x with the given value of the x?
>
> All tips are very welcome. Cheers!


I am new as well to Matlab but I think you may have to
create a script file if you want multiple outputs for the
function file.

In article <fv7c9h$ooh$1@fred.mathworks.com>,
Matt Carroll <matthew-carroll@utc.edu> wrote:

>I am new as well to Matlab but I think you may have to
>create a script file if you want multiple outputs for the
>function file.

No, that isn't the case. To have multiple outputs for a function,
list all the outputs on the left hand side before the '=' . For example,

function [x y] = rotate45(oldx, oldy)


You would call upon this by (for example):

[newx, newy] = rotate45(17.3, 12.8);

--
  "All is vanity." -- Ecclesiastes

roberson@ibd.nrc-cnrc.gc.ca (Walter Roberson) wrote in
message <fv7dhm$rm9$1@canopus.cc.umanitoba.ca>...
> In article <fv7c9h$ooh$1@fred.mathworks.com>,
> Matt Carroll <matthew-carroll@utc.edu> wrote:
>
> >I am new as well to Matlab but I think you may have to
> >create a script file if you want multiple outputs for the
> >function file.
>
> No, that isn't the case. To have multiple outputs for a
function,
> list all the outputs on the left hand side before the '='
. For example,
>
> function [x y] = rotate45(oldx, oldy)
>
>
> You would call upon this by (for example):
>
> [newx, newy] = rotate45(17.3, 12.8);
>
> --
> "All is vanity." --
Ecclesiastes

fun(f,x,dx)

f(x)=ln(x), x=2, dx=0.01 %these the given values

f?(x)=1/x %the derivative of the function = output1

f'(2)=1/2 %the derivative of the function with the given
value of 2 = output2

df1=f?(x)*dx %the estimated value of the differential

df1=0.0050 %is this = output3

df2=f(x+dx)-f(x) %the exact value of the differential

df2=0.004987 %is this = output4

Could someone give me an example how I could compile this to
a m.file in matlab? I know how to do it on paper but I have
no idea how to do it as an m.file in matlab.

fun(f,x,dx)

f(x)=ln(x), x=2, dx=0.01 %these the given values

f?(x)=1/x %the derivative of the function = output1

f'(2)=1/2 %the derivative of the function with the given
value of 2 = output2

df1=f?(x)*dx %the estimated value of the differential

df1=0.0050 %is this = output3

df2=f(x+dx)-f(x) %the exact value of the differential

df2=0.004987 %is this = output4

Could someone give me an example how I could compile this to
a m.file in matlab?