![]() Note that artists whose label start with an underscore are ignored when legend() is called with no argument. In legend(), we specify title and handles by extracting legend elements from the plot. I have made a simple scatterplot using matplotlib showing data from 2 numerical variables (varA and varB) with colors that I defined with a 3rd categorical. We can try to add legend to the scatterplot colored by a variable, by using legend() function in Matplotlib. Make sure to specify the values to be colormapped via the c argument.Īnd WARNING:matplotlib.legend:No artists with labels found to put in legend. Add Color to Scatterplot by variable in Matplotlib. (x, y, sNone, cNone, markerNone, cmapNone, normNone, vminNone, vmaxNone, alphaNone, linewidthsNone,, edgecolorsNone, plotnonfiniteFalse, dataNone, kwargs) source. Occasionally in my trial and error i get the following messages:- UserWarning: Collection without array used. I also tried handles = scatter.legend_elements()Īx.legend(title='ABC', handles=handles, labels=colour_names) The scatter gets printed properly but without the legend `plt.legend(handles=scatter.legend_elements(), I've tried the following ways to add the legend, but it neither gives an error, nor an output. Scatter = plt.scatter(x,y, c = colormap, s = 5)` x = np.array(df)Ĭolormap = np.array()Ĭolour_names = The variable colour_names has the labels that I want to add to the legend.įollowing is the code to create the scatter chart. I want a title of the legend and the legend should be in 1 row and not in multiple rows, I also want to add labels to the legend. I have successfully generated the scatter chart, however I am finding it difficult to mention the legend on the plot. The points have 4 colours: light blue for values less than 2, blue for 2-4, orange for 4-6 and brown for 6 and above. I guess you meant to say that the legend_elements of scatter1 is empty, right? Matplotlib backend ( print(matplotlib.get_backend())): 'module://_inline'.The first legend does not contain anything, since the legend_elements of scatter1 is empty.I have created a scatter chart where I have values of a certain column ABC ranging from 0-10. MacQueen developed the k-means algorithm in 1967, and since then, many other implementations and algorithms have been developed to perform the task of grouping data. ![]() my example was slightly different before posting. 9 min read Clustering sure isn’t something new. That is expected, and there is a warning about it. \matplotlib\collections.py:960: UserWarning: Collection without array used. Make sure to specify the values to be colormapped via the c argument. This argument accepts both hex codes and normal words. ![]() In what other manner could I use the c argument then? I found this warning not helpful because I was using the same parameter in both examples You can also change the color of the data points within a matplotlib scatterplot using the color argument. The reason is that in case you specify the scatter colors as a simple list of colors, no mapping is happening, and therefore we cannot know what to show in the legend (other than maybe the color itself?). pyplot.scatter allows for passing to c an array that corresponds to groups, which will then color the points based on those groups. import matplotlib.pyplot as plt from numpy.random import rand fig, ax plt.subplots() for color in 'red', 'green', 'blue': n 750 x, y rand(2, n) scale 200.0 rand(n) ax.scatter(x, y, ccolor, sscale, labelcolor, alpha0.3, edgecolors'none') ax.legend() ax.grid(True) plt. ![]() Possibly we might think about extending the functionality, but for this it would be good to collect use cases. can you tell what exactly you would expect the legend to show in the above example case? However, this seems to not support generating a legend without specifically plotting each group separately. What would be helpful for me is that the list of lines is returned so i can map the labels by myself.īut maybe I am just using scatter incorretly in this instace. Is it possible to provide a list of classes (instead of colors) and then pass a dict like mapping with class -> color?įrom lors import from_levels_and_colorsĬ = np.random.randint(0, n_cats, n).astype(str) What I would like to do is create a scatter plot with custom colors for every class, with a corretly labeled legend and not use loops and the label argument. ![]() U, inv = np.unique(c, return_inverse=True)įor cat, color in zip(u, plt.cm.viridis(np.linspace(0,1,len(u)))):Īx.scatter(x, y, color=color, label=cat)Īx.plot(x, y, color=color, ls="", marker="o", label=cat)Ĭmap, norm = from_levels_and_colors(np.arange(0,len(u) 1)-0.5, plt.cm.viridis(np. ![]()
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