On Sun, Jun 29, 2008 at 6:10 PM, Tony S Yu <[EMAIL PROTECTED]> wrote: > Hi. A couple of questions about `scatter`: > Q1 > ==== > The bounding box `axes.dataLim` increases in size when calling scatter(x, y) > compared to plot(x, y) (for the same x, y data, of course). I think this > change is due to the size of the markers being added to the data limits (not > sure if this is true). Is there an easy way to get the same data limits I > would have for a call to `plot`?
I think your explanation is correct (the size of the markers are included in scatter (and patches in general) but not for plot (and lines in general). There is no *easy* way, but you could maintain your own bbox instance and update it in the same way the Axes._update_datalim* methods do. (See Axes._update_patch_limits and Axes._update_line_limits for example) > Q2 > ==== > Is there a way to get the data from the axes of a scatter plot? > Initially I thought I could get it with: >>>> for collection in ax.collections: >>>> for path in collection._paths: >>>> print path.vertices > But this seems to be the path that draws the scatter markers. Any ideas? The "offsets" of the collection are the x and y locs, and the vertices are the marker path, as you observed. We do not have a "publicly accessible" api for accessing the offsets (they are stored as col._offsets where col is the collection instance), but you could add an spi (get_offsets, set_offsets, etc... > Frame Class > ========== > Finally, if anyone is interested, I'm playing around with a Frame class for > `axes.frame`. This class adds customizable axes frames similar to the topic > of this thread: > http://sourceforge.net/mailarchive/message.php?msg_id=87d57vjgye.fsf%40peds-pc311.bsd.uchicago.edu > In this older thread, the SAGE axes frames were criticized for not being > flexible enough. I've tried to make this class as general as possible > (within my ability:). As an example of the flexibility of this Frame class, > I've added some Tufte-style frames similar to: > http://hupp.org/adam/weblog/2007/09/03/etframes-applying-the-ideas-of-edward-tufte-to-matplotlib/ > To the developers on this thread: If there's anything I could do to make the > attached Frame class more flexible (and more suitable for possible inclusion > into MPL), I'd be happy to get some feedback. We are *definitely* interested in this. It has some features I am less interested in, and is missing some of the features I am very interested in. In the former camp, some of the Tufte ideas have a place somewhere, and the frame class (or extensions thereof) is probably the right place for them, but I don't consider these to be the core limitations of the current frame handling. Don't get me wrong, I am a big Tufte fan, have all of his books, have attended his lecture, am into his ideas, etc. I just don't consider the lack of such features to be the major problem with the current impl. The two major problems as I see them are: 1) the ability to just draw part of the frame, which you've partly addressed, and 2) the ability to put the frame (and associated ticks and labels) where you want, which is still lacking. I'd like the user to be able to say: draw the y axis at such-and-such a loc in such-and-such coords (axes or data) and have the ticks and labels come along for the ride. As you've noticed, this takes a bit more work. Ideally, one could have one or more of these (the current top and bottom for the x axes would then just be two incarnations) with (possibly) separate tickers and formatters. Because this goes to the core plotting functionality, it is not easy either from a design or implementation standpoint, particularly within the constraints of backward compatabiliity, but it is a problem well worth solving. It's been on the wish list a long time. I'd love for you to take the lead on this. Given my (and other developers) constraints on time, we'll have only limited time to help, but hopefully we can give you some pointers when you get stuck. > Current Limitations: > ================ > * the frame can only be placed on the borders of the axes (mainly because I > don't know how to move the tickers anywhere else). Look at how the transforms are set in the axis.Axis class for the tickers - the ticks and labels have "blended transforms" which blend data coords and axes coords. Eg, the x axis has the x location in data coords and the y location in axes coords (0 for the bottom and 1 for the top). For example, for default rectilinear coords, this transformation is built by the Axes instance: self._xaxis_transform = mtransforms.blended_transform_factory( self.axes.transData, self.axes.transAxes) and accessed via def get_xaxis_transform(self): """ Get the transformation used for drawing x-axis labels, ticks and gridlines. The x-direction is in data coordinates and the y-direction is in axis coordinates. .. note:: This transformation is primarily used by the :class:`~matplotlib.axis.Axis` class, and is meant to be overridden by new kinds of projections that may need to place axis elements in different locations. """ return self._xaxis_transform > * RangeFrame only works with linear data (I'm not sure how to use the > `axes.transScale` to properly transform the data) > * RangeFrame and DashDotFrame don't work properly with `scatter` (because of > the questions in this post). > The frame class itself isn't too long, but I got a little carried away > adding in extra crap. > Sorry for the long, rambling email.;) No problem -- this is a complicated part of the code that is not particularly flexible or extensible. It would be extremely useful if you could develop and extensible API for axis handling (so one could incorporate some of these Tufte extensions and related ideas at the *user* level even if they are not built in, though we'd probably supply some by default or by example) that also solves the core problem of letting the user draw the axis (one or more) where they want. SAGE, for example, had to hack an entirely separate axis implementation (with their own tick lines and labels) just to draw them in the center mathematica style. Keep us posted! JDH ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
