[Qgis-user] Principal Component Analysis ?

[Falk Huettmann]

Hi there,

in my view and if I may comment here:
while R is scary (as stated below),  so are probably many of the wrapped R
packages really,
PCAs are even more scary, and their underlying mindsets,
and the real horror starts when such things get
implemented into 'homebrews' and such tools, or
into QGIS and just as point and klick.

As a rule, I would highly suggest to stay clear of such efforts and
concepts.
It's no good science, and not much defendable. Unless well thought out,
it harms the product and reputation you want to create.
(for a bad example see Krigging in some major commercial GIS...
 We have seen such things many places).

There should first be a good debate about statistics, if pursued as tools
in QGIS etc.
Arguably, unless it's predictive (for inference etc) it has no much value
these days anymore.

Agreed,
it's a tragedy of our time that such old things still happen, all the time,
and in the sciences.
But it ain't no good, really, and is no good progress. My word for it.

(I also agree that it is good to keep avenues open for such
work, as an option and for people who know what they are doing and why;
sure.
But not more than that. Many bad examples exist all over for decades)

Feel free to follow up as needed; kind regards
   Falk Huettmann
     Uni of Alaska Fairbanks


On Fri, Jun 23, 2017 at 10:57 AM, Nicolas Cadieux <
nicolas.cadieux at archeotec.ca> wrote:

> Hi,
> You can use R for PCA.
> Use the R Commander package to add a GUI.  R can be scary at first.
> Nicolas
>
> Le 23 juin 2017 à 11:03, image [via OSGeo.org] <[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=5325361&i=0>> a écrit :
>
> Good afternoon,
>
> i'm working on windows with several opensource tools (qgis, otb,
> grass...),
>
> I generated several OTB texture indices. Now, i want to evaluate the
> information 's redundancy thanks to a Principal Component Analysis.
>
> => Is it possible to do that with some opensource tools (otb? qgis?
> grass?) Moreover, I would like set a mask AND set a spectral subset (in
> order to ignore some indices bands which seems "strange" and not relevant
> to introduce into the process).
>
> Could you throw light for me?
>
> In advance, thank you very much for your help.
>
> Kind regards.
>
> ------------------------------
> If you reply to this email, your message will be added to the discussion
> below:
> http://osgeo-org.1560.x6.nabble.com/Principal-
> Component-Analysis-tp5325338.html
> To start a new topic under QGIS - User, email [hidden email]
> <http:///user/SendEmail.jtp?type=node&node=5325361&i=1>
> To unsubscribe from QGIS - User, click here.
> NAML
> <http://osgeo-org.1560.x6.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml>
>
>
> ------------------------------
> View this message in context: Re: Principal Component Analysis ?
> <http://osgeo-org.1560.x6.nabble.com/Principal-Component-Analysis-tp5325338p5325361.html>
> Sent from the QGIS - User mailing list archive
> <http://osgeo-org.1560.x6.nabble.com/QGIS-User-f4125267.html> at
> Nabble.com.
>
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20170623/44eb6286/attachment.html>