John,

It's been a little while since I installed QGIS on my machine, but I wonder
if you missed a selection somewhere in the installation process. Can you
reinstall QGIS? (i.e. do you have admin permissions?) There might be a
number of selections you can make when installing, and my guess is that you
missed a selection to have the proper Python libraries installed. Maybe
there is a "Full" installation option, which puts everything on your
machine. As I said on my installation of QGIS, that code works just fine,
and I'm certain that I haven't done anything special post-install.

Ryan

On Thu, Feb 12, 2015 at 12:37 PM, john polo <jp...@mail.usf.edu> wrote:

>  Ryan,
> I used the first line of your example and this was the result:
> Traceback (most recent call last):
>   File "<input>", line 1, in <module>
>   File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 454, in _import
>     mod = _builtin_import(name, globals, locals, fromlist, level)
> ImportError: No module named matplotlib.pyplot
>
> I'm not sure what the first command is to confirm whether a module is
> installed or not, but it looks like I may need that.
> Thanks, Ben and Ryan.
>
> John
>
>
> On 2/12/2015 10:09 AM, Ryan Nelson wrote:
>
> John,
>
>  As Ben said, the QGIS Windows installer comes with its own Python
> installation, which doesn't know anything about any other Python install.
> Unfortunately, this apparently makes it rather difficult to install other
> packages. However, QGIS Python already contains Numpy and Matplotlib and
> PyQt4, which is what you need here. From the Plugins dropdown menu, select
> Python Console. In the console that opens at the bottom of the screen, you
> should be able to type (don't type the > characters):
> >>> import matplotlib.pyplot as plt
> >>> plt.plot([1,2,3])
> >>> plt.show()
>
>  On my install of QGIS, that opens a pop-up window with a plot of those
> data points. Does this throw an error for you too?
>
>  Ryan
>
> On Thu, Feb 12, 2015 at 10:35 AM, john polo <jp...@mail.usf.edu> wrote:
>
>> Users,
>> I am working on Windows 7 with QGIS 2.4. I am trying to get a plugin
>> installed in QGIS called Semi-Automatic Classification Plugin to work.
>> The plugin is demonstrated here:
>>
>> http://fromgistors.blogspot.com/2013/07/working-with-multispectral-bands-in-qgis.html
>>
>> The first time I tried to install the QGIS plugin, I got an error
>> message that backend_qt4agg was not installed. I installed Python(x,y)
>> with Python 2.x, because it seemed like the easiest way to get
>> matplotlib and a bunch of other apps/extensions installed at the same
>> time with minimal effort. I am not a programmer and I'm not familiar
>> with installing things from source and then configuring settings. After
>> the Python(x,y) install, I went to QGIS and started again and tried to
>> install the plugin. I got the same error message. Please tell me what I
>> need to do to get this backend installed in order to get the QGIS plugin
>> I want.
>>
>> John Polo
>>
>>
>>
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