Increase the "precision" of a heatmap

Question

Using seaborn i am generating heatmaps for various series of a DataFrame.

The main code that I use is the following:

def plot_heatmap(data, cmap, x_label, y_label, y_ticks = None):

    fig, ax = plt.subplots()

    heatmap = sns.heatmap([data], robust=True,cmap=cmap, annot=False, cbar_kws={"label": "Value"}, ax=ax)

    ax.set_xlabel(x_label)
    ax.set_ylabel(y_label)
    if y_ticks:
        heatmap.set_yticklabels([y_ticks])

    plt.show()

And it's invoked per case that I have (for each Pandas.Series). My issue is that the generated result looks like this:

But the thing is, that this looks somewhat deceiving. I generated the following random dataset for this plot: gist for dataset.

The number of zeroes as you see is 1. But someone, observing this plot would think otherwise.

So, how could I improve this plot to make it more accurate? I tried various cmaps like:

    cmap = sns.diverging_palette(220, 10, as_cmap=True) 
    cmap2 = sns.diverging_palette(250, 0, sep=1, n=256, as_cmap=True)
    cmap3 = 'gist_rainbow'
    ...

But I didn't quite get the desired result. Thank you in advance!

Answer 1

You have a massive range of scales. You can try plotting a logarithm of the data:

plot_heatmap(np.log10(df.data), cmap="plasma", x_label="asdf", y_label="asdf")

You can bin your data and plot the bins/categories. E.g. values between 0 and 10 are one colour, values larger than 1e20 are another. You can define the bins in any way that suits your dataset or what you want to show. In the first example below I create 20 equally spaced bins in log10 space.

bins = np.logspace(np.log10(0.1), np.log10(df["data"].max()), 20)
labels = np.arange(1, len(bins))

df["binned"] = pd.cut(df["data"], bins=bins, labels=labels)

plot_heatmap(df["binned"], cmap="magma", x_label="asdf", y_label="asdf")

And here I manually define values for the bins:

bins = [-1, 100, 1e6, 1e9, df["data"].max()]
labels = np.arange(1, len(bins))

df["binned"] = pd.cut(df["data"], bins=bins, labels=labels)

plot_heatmap(df["binned"], cmap="magma", x_label="asdf", y_label="asdf")