Finding the gradient of a graph

Having installed Octave I now want to find gradients of gradients of gradients...... of gradients.

This is a note to remind me to do this.

So, turns out there is a function which does this:
gradient(F)

so, here's me plotting a sine wave, and then drawing gradients of that graph:


x=0:0.1:20
y=sin(x)

plot(y)
hold all
plot(gradient(y)*10)
hold all
plot(gradient(gradient(y))*100)
hold all
plot(gradient((gradient((gradient(y)*10))*10))*10)
plot(gradient((gradient((gradient((gradient(y)*10))*10))*10))*10)

installing Octave on Mac OS X 10.6 and 10.7

So, just read the wiki here. As it's open source, they havent yet made a pkg installer for it. Apparently, the best thing to do is to use a Package Manager to install it for you.

I've just tried Fink but the website isn't working. Looks like they've moved their website to http://fink.thetis.ig42.org/. Apperantly there's no pkg installer for this either! Here's the download for the binary.

I gave up here and found that MacPorts have an installer.

Installed MacPorts alright, but when I tried to run the command:

sudo port install octave-devel +atlas+docs

It came up with the error not knowing what the command "port" was. I had to type in:

export PATH=/opt/local/bin:/opt/local/sbin:$PATH

One prerequisite is to have xcode installed.

Having done all this, still came up with an error:

Error: Port octave-devel not found

I think it's because we have a proxy server which looks like complicated to add to MacPorts!

Oh well, might just try Matlab! (student version £55!)


....... a little time later......

So I'm now trying at home on OS X 10.7.5

Installed MacPorts
trying to install octave but comes up with:

Error: Port octave not found

Turns out you have to selfupdate MacPort in order for it to sync something or other. Type:

sudo port -v selfupdate

This then came up with the error:

rsync: failed to connect to rsync.macports.org: Connection refused (61)

rsync error: error in socket IO (code 10) at /SourceCache/rsync/rsync-42/rsync/clientserver.c(105) [receiver=2.6.9]

Command failed: /usr/bin/rsync -rtzv --delete-after rsync://rsync.macports.org/release/tarballs/base.tar /opt/local/var/macports/sources/rsync.macports.org/release/tarballs

Exit code: 10

Error: /opt/local/bin/port: port selfupdate failed: Error synchronizing MacPorts sources: command execution failed

Doh! Just did a search and found this. Turns out I have PeerGuardian running. Turned it off and ran selfupdate again which worked fine. So, next I tried installing octave again:

sudo port install octave

--->  Computing dependencies for octave

Error: Dependency 'atlas' not found.

Doh! I read this article which tells how other people are having the same trouble. Looks like one of the sync files on a server must be wrong. selfupdating port at some point will fix it;

sudo port -v selfupdate
sudo port install octave +accelerate +gcc45

What do you know? It worked!!