A similiar question has been asked recently as How to make GRASS and SAGA tools capable to use in QGIS？
However I have some specific queries and process I have tried which are probably better in a new question for clarity.
The process I used is as follows:
- Installed QGIS using OSGeo4W. Installed Dufour 2.1 under Program files. Apps directory shows saga_gui.exe (2.0.8). Grass plugin working ok. Install looks ok.
- The SAGA instructions mention a configuration dialogue without being a bit more accurate. https://www.qgis.org/en/docs/user_manual/processing/3rdParty.html. I assume this is in QGIS Settings \ Options \System variables, and that you should be able to put in the path to the .exe? If so I cannot seem to get this to work. Or maybe it's somewhere else.
- Also mentioned is that SAGA 2.1 is needed. I've downloaded this and, as it appears to be a "standalone programme", put the whole thing into the Dufour folder rather than reinstalling everything with the aim of configuring the path to the .exe from QGIS. Is this correct, as usually installs put files all over the place?
From my quick look at the program SAGA seems to look pretty good. However there appears to be only basic file support (dxf, txt, etc) and no ability to directly load MapInfo files which is what I was interested in.
How do I run it from QGIS?