matplotlib-users

[Matplotlib-users] Fwd: Re: Colobar and change axis x and y labels

[<Pyt...@ro...>]

Thanks Alexa and Jerzy.

other questions? ... Here they are:

- changing to an image grey scale only needs ... what?

- I need to do a 'plane fit' of the image. Does matplotlib
   have some routine for this? Or shall I use other math libs?

Thanks again.


>  Le 16/02/2012 02:20, Alexa Villaume a écrit :
>>  Try using 'xticks' and 'yticks', those commands let you define the
>>  location and label fo your tick marks.
>>
>  This *alone* will not do, the image might be scaled badly. Add extent.
>
>  Try this:
>
>  fig   = plt.figure()
>  frame = plt.subplot(111)
>  im=frame.imshow(data,extent=[0,3400,0,3400])
>  plt.xticks([0,3400]); plt.yticks([0,3400])
>  plt.xlabel('X (nm)')
>  plt.ylabel('Y (nm)')
>  plt.colorbar(im)
>
>  plt.show()
>
>  ==
>
>  Jerzy Karczmarczuk
>  Caen, France
>
>
>  ------------------------------------------------------------------------------
>  Virtualization&   Cloud Management Using Capacity Planning
>  Cloud computing makes use of virtualization - but cloud computing
>  also focuses on allowing computing to be delivered as a service.
>  http://www.accelacomm.com/jaw/sfnl/114/51521223/
>  _______________________________________________
>  Matplotlib-users mailing list
>  Mat...@li...
>  https://lists.sourceforge.net/lists/listinfo/matplotlib-users

Re: [Matplotlib-users] Fwd: Re: Colobar and change axis x and y labels

[Alexa V. <ale...@gm...>]

You need to use the 'imshow' function to display an image in greyscale. You
have to turn your image into an array of values and then put that array
into imshow with the colormap set to grey.

I don't know about how to do a plane fit...

On Wed, Feb 15, 2012 at 9:18 PM, <Pyt...@ro...> wrote:

>
> Thanks Alexa and Jerzy.
>
> other questions? ... Here they are:
>
> - changing to an image grey scale only needs ... what?
>
> - I need to do a 'plane fit' of the image. Does matplotlib
>   have some routine for this? Or shall I use other math libs?
>
> Thanks again.
>
>
> >  Le 16/02/2012 02:20, Alexa Villaume a écrit :
> >>  Try using 'xticks' and 'yticks', those commands let you define the
> >>  location and label fo your tick marks.
> >>
> >  This *alone* will not do, the image might be scaled badly. Add extent.
> >
> >  Try this:
> >
> >  fig   = plt.figure()
> >  frame = plt.subplot(111)
> >  im=frame.imshow(data,extent=[0,3400,0,3400])
> >  plt.xticks([0,3400]); plt.yticks([0,3400])
> >  plt.xlabel('X (nm)')
> >  plt.ylabel('Y (nm)')
> >  plt.colorbar(im)
> >
> >  plt.show()
> >
> >  ==
> >
> >  Jerzy Karczmarczuk
> >  Caen, France
> >
> >
> >
>  ------------------------------------------------------------------------------
> >  Virtualization&   Cloud Management Using Capacity Planning
> >  Cloud computing makes use of virtualization - but cloud computing
> >  also focuses on allowing computing to be delivered as a service.
> >  http://www.accelacomm.com/jaw/sfnl/114/51521223/
> >  _______________________________________________
> >  Matplotlib-users mailing list
> >  Mat...@li...
> >  https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>
>
>
>
> ------------------------------------------------------------------------------
> Virtualization & Cloud Management Using Capacity Planning
> Cloud computing makes use of virtualization - but cloud computing
> also focuses on allowing computing to be delivered as a service.
> http://www.accelacomm.com/jaw/sfnl/114/51521223/
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>

Re: [Matplotlib-users] Fwd: Re: Colobar and change axis x and y labels

[Jerzy K. <jer...@un...>]

"Pythphys", would it be too demanding to ask you to sign your messages 
with a human name?...
Danke.

You ask:

> - changing to an image grey scale only needs ... what?
plt.set_cmap(plt.cm.gray)

in the context of your current figure. Or, use cmap=... in your imshow.
Please, look up "colormap" in the documentation.

> - I need to do a 'plane fit' of the image. Does matplotlib
>     have some routine for this? Or shall I use other math libs?

I am not a guru of matplotlib, but this is a visualisation package, not 
a data processing one. Scipy (numpy) have some interpolation procedures, 
polyfit, etc. but I don't remember without digging the docs (which you 
might do as well) whether multidimensional fitting is there.

Anyway, why not use your head? This is a standard student exercise.

You need to fit:   zf = ax + by + c, having z =f(x,y) in your image, am 
I right? If not, forget the rest.

Use the linear regression, find the zero of the gradient wrt (a,b,c) of

SUM[(ax +by +c - z)^2]

and that's all.

The most tragic part of the exercise is the necessity of solving a 
linear equation set in 3 variables...

Jerzy Karczmarczuk
Caen, France