I have been using the Altair python API for a Data Visualization project, and everything went smoothly until I wanted to add a radar chart to my app.
I could not find anything on Altair's python API documentation about radar charts, however there seems to be an entry about that in Altair's core documentation but I couldn't access it.
I saw that plotly had that feature but I would really have liked using only one plotting framework...
Is there really no way to make a radar chart with Altair in python ?
This is currently not implemented in VegaLite, you can see the discussion in these two issues and open a new one if you think there is a good case to be made for radar charts:
https://github.com/vega/vega-lite/issues/3805
https://github.com/vega/vega-lite/issues/408
In Altair you might be able to hack something together by layering multiple mark_arc charts with a fillOpacity=0 and a colored stroke (although I don't think this will work since I can't see any way to get right of the lines going towards the middle.
I have a system written in C++ that do some processing on some input video. As a result of this processing I get some statistics .
Right now the system produces number data that is saved on a text file.
Later I have written some python script that takes these numbers and shows some plots.
I was thinking, it would be nice if I can put this info in the video.
If it is just numerical values I can do that easily with the text writing functions in OpenCV.
However, perhaps it would be nice to include a small plot in the video.
How can I do that? Does OpenCV has something of this sort?
I also found this question about plotting with C++. I wonder if some answers there could be of any help. (As you can see the nature of the question although related is a bit different)
I am thinking I can go in one of two ways:
Implementing this plotting and then embedding the plot directly in my C++ code immediately after finding the values
or
Processing the video, getting the values in a text file as now, and then processing this text file, the video in Python to embed a plot in it
The key concept here is embedding a small plot in a video. How can I do that in either C++ or python?
I'm wondering if it is possible to plot a vertex as image (loaded from a file or directly) in Igraph. Any ideas?
This is definitley possible in the R version of iGraph using the raster function, however a brief search did not reveal any implementation of this function in Python (it's not in the igraph documentation anyway).
If this is essential to your work, then I would consider switching to R, or possibly another tool such as Gephi. For Python, however, you might consider using something like pyvis. This package is small but powerful in terms of visualization. I've been playing around with it over the past few days and its very easy to display a graph with pictures as nodes, and it comes with the added benefit of providing interactive functioning. Take a look at the tutorial here, which will highlight what this package can provide.
What I want to do is to generate a static image (e.g. a png) using python and using openstreetmap tiles as a background.
Mathplotlib and Basemap is almost what I'm looking for. The problem is being able to use OSM tiles as background. I'm not pleased by the approach suggested in http://stevendkay.wordpress.com/2010/02/24/plotting-points-on-an-openstreetmap-export/
The closest I found is in this answer but using R, and not python Plotting points from a data.frame using OpenStreetMap
Did I miss any obvious and easy solution?
Thanks for your help
EDITÂ : this questions suggests many tools, but none seems to match my needs How can I display OSM tiles using Python?
You overlooked the "Export" tab at the OSM website, which is capable of generating a static image with the dimensions and map extents you want. Have a look at http://wiki.openstreetmap.org/wiki/Export
Please be advised that generating static images is a resource-intensive process, and the OSM sysadmins will frown upon you if you do a large number of requests or abuse this feature. Unfortunately this means you'll have to find another solution if you're trying to do lots of images.
By the way, the data you're plotting on top is properly projected into EPSG:3857 and not just raw lat/lon coordinates, right? Raw lat/lon data will look distorted at large zoom levels.
I have a large data set of tuples containing (time of event, latitude, longitude) that I need to visualize. I was hoping to generate a 'movie'-like xy-plot, but was wondering if anyone has a better idea or if there is an easy way to do this in Python?
Thanks in advance for the help,
--Leo
get matplotlib
The easiest option is matplotlib. Two particular solutions that might work for you are:
1) You can generate a series of plots, each a snapshot at a given time. These can either be displayed as a dynamic plot in matplotlib, where the axes stay the same and the data moves around; or you can save the series of plots to separate files and later combine them to make a movie (using a separate application). There a number of examples in the official examples for doing these things.
2) A simple scatter plot, where the colors of the circles changes with time might work well for your data. This is super easy. See this, for example, which produces this figure
alt text http://matplotlib.sourceforge.net/plot_directive/mpl_examples/pylab_examples/ellipse_collection.hires.png
I'd try rpy. All the power of R, from within python.
http://rpy.sourceforge.net/
rpy is awesome.
Check out the CRAN library for animations,
http://cran.r-project.org/web/packages/animation/index.html
Of course, you have to learn a bit about R to do this, but if you're planning to do this kind of thing routinely in future it will be well worth your while to learn.
If you are interested in scientific plotting using Python then have a look at Mlab: http://code.enthought.com/projects/mayavi/docs/development/html/mayavi/mlab.html
It allows you to plot 2d / 3d and animate your data and the quality of the charts is really high.
Enthought's Chaco is designed for interactive/updating plots. the api and such takes a little while to get use to, but once you're there it's a fantastic framework to work with.
I have had reasonable success with Python applications generating SVG with animation features embedded, but this was with a smaller set of elements than what you probably have. For example, if your data is about a seismic event, show a circle that shows up when the event happened and grows in size matching the magnitude of the event. A moving indicator over a timeline is really simple to add.
Kaleidoscope (Opera, others maybe, Safari not) shows lots of pieces moving around and I found inspirational. Lots of other good SVG tutorial content on the site too.
You might want to look at PyQwt. It's a plotting library which works with Qt/PyQt.
Several of the PyQwt examples (in the qt4examples directory) show how to create "moving" / dynamically changing plots -- look at CPUplot.py, MapDemo.py, DataDemo.py.