vastcenters.blogg.se - Matplotlib scatter marker size

If the figure dpi is different (matplotlib default is fig.dpi=100), 1 point = fig.dpi/72. If the figure dpi is 72 as well, one point is one pixel. It might be useful to be able to specify sizes in pixels instead of points. The standard size of points in matplotlib is 72 points per inch (ppi) - 1 point is hence 1/72 inches.

Also linewidths is often specified in points. Points are often used in typography, where fonts are specified in points. So far the answer to what the size of a scatter marker means is given in units of points. doubling the underlying quantity should double the area of the marker. Specifying the size of the scatter markers in terms of some quantity which is proportional to the area of the marker makes in thus far sense as it is the area of the marker that is perceived when comparing different patches rather than its side length or diameter. This is the motivation to call it "area" even though in most cases it isn't really. In all cases however the area of the marker is proportional to the s parameter.

For other markers there may not even be any obvious relation to the area of the marker.

For a circle, the area of the circle is area = pi/4*s.

For the special case of a square marker, marker="s", the area of the marker is indeed directly the value of the s parameter.

Of course the units of points**2 are area units. So why do other answers and even the documentation speak about "area" when it comes to the s parameter? In order to produce a scatter marker of the same size as a plot marker of size 10 points you would hence call scatter(. So the relationship between the markersize of a line plot and the scatter size argument is the square. In order to obtain a marker which is x points large, you need to square that number and give it to the s argument. S : scalar or array_like, shape (n, ), optional The argument s in plt.scatter denotes the markersize**2. Plt.legend(loc='center left', bbox_to_anchor=(1.1, 0.5), labelspacing=3)īecause other answers here claim that s denotes the area of the marker, I'm adding this answer to clearify that this is not necessarily the case. Thus if we want a circle to appear a factor of n bigger we would increase the area by a factor n not the radius so the apparent size scales linearly with the area.Įdit to visualize the comment by is what it looks like for different functions of the marker size:

However it is the second example (where we are scaling area) that doubling area appears to make the circle twice as big to the eye. Similarly the second example each circle has area double the last one which gives an exponential with base 2. The question asked about doubling the width of a circle so in the first picture for each circle (as we move from left to right) it's width is double the previous one so for the area this is an exponential with base 4. Now the apparent size of the markers increases roughly linearly in an intuitive fashion.Īs for the exact meaning of what a 'point' is, it is fairly arbitrary for plotting purposes, you can just scale all of your sizes by a constant until they look reasonable.Įdit: (In response to comment from probably confusing wording on my part. If instead we have # doubling the area of markers Notice how the size increases very quickly. To see this consider the following two examples and the output they produce. Because of the scaling of area as the square of width, doubling the width actually appears to increase the size by more than a factor 2 (in fact it increases it by a factor of 4). There is a reason, however, that the size of markers is defined in this way. This means, to double the width (or height) of the marker you need to increase s by a factor of 4.

This can be a somewhat confusing way of defining the size but you are basically specifying the area of the marker.