Different coloured regions on a scatter plot

I have a g-g diagram where I want to display different regions in different colours (so right acceleration is one colour, pure acceleration is a different one, left acceleration is different, pure left cornering is different and so on). I was able to overlay a plot on top to show left, right and in the middle like this:

sz = 8

scatter(Lat_A, Long_A, sz, 'filled')
ylabel("Longitudinal Acceleration /g")
xlabel("Lateral Acceleration /g")

threshold = 0.4
right = Lat_A(Lat_A>threshold)
left = Lat_A(Lat_A<-threshold)

hold on;
scatter(right, Long_A(Lat_A > threshold), sz, 'g', 'filled'); 
scatter(left, Long_A(Lat_A < -threshold), sz, 'r', 'filled'); 
hold off;

However, I'm struggling to factor in the braking and acceleration the same way on the same plot. In simple terms, I want to show (x>0.4, y>0.4), (x<-0.4, y>0.4), (abs(x)< 0.4, y>0.4) etc. as different colours. I'm pretty new to MATLAB so any help would be appreciated.

Answer 1

[Star Strider]

Depicting regions such as: '(x>0.4, y>0.4), (x<-0.4, y>0.4), (abs(x)< 0.4, y>0.4) etc.' would require a patch plot. These can be overlaid with your current plot, however it would be best to change the 'FaceAlpha' property to something less than 1 in order to show the other data clearly. (I had to look up 'g-g diagram.)

I am not certain what you want to do, however something like this could work --

figure
patch([-4 0 0 4], [4 0 0 4], 'g', FaceAlpha=0.5, EdgeColor='none')
axis([-5 5 -1 5])
grid

The patch arguments have to describe a closed region, so at least 4 values for each one.

.

[Felicity]

Sorry I forget not everyone is a motorsport nerd. To put it in context, I'm doing an analysis to see lateral vs longitudinal acceleration recorded by a race car over the course of 1 lap of a circuit.

This is an image of a different one I found online that I think illustrates what I want a bit better (although I don't need the lines around or between the colours, just colouring the points would be enough). The only thing is I want to have the points in each region stored somehow so I can then see how many fall within each region. That way I can see what % of the lap time was spent doing each activity.

Thank you very much for the response, I'll have a play around with your suggestions.

[Star Strider]

Airplanes for me. I'm an Instrument-Rated Private Pilot, so cars only to get to and from the airport!

'The only thing is I want to have the points in each region stored somehow so I can then see how many fall within each region

See if the inpolygon function does what you want. (I'm still not absolutely certain what that is.)

For the region colours, I still recommend patch.

EDIT -- (11 Sep 2026 at 00:23)

Using inpolygon to determine the points inside and outside a region, then plotting them --

t = linspace(0, 2*pi, 500).';
r = 1;
c = r.*[cos(t) sin(t)];
datax = randn(250,1);
datay = randn(250,1);

[in,on] = inpolygon(datax, datay, c(:,1), c(:,2));
nron = nnz(on)

nron = 0

figure
plot(c(:,1), c(:,2), DisplayName='Region of Interest')
hold on
scatter(datax(in), datay(in), '.g', DisplayName='In Region')
scatter(datax(~in), datay(~in), '.r', DisplayName='Outside of Region')
if nron ~= 0
    scatter(datax(on), datay(on), '.m', DisplayName='On Border')
end
hold off
grid
axis('equal')
xlabel('X')
ylabel('Y')
legend(Location='best')
pctpoints = nnz(in)/size(datax,1) * 100;
title(sprintf('Region Contains %.2f%% Of The Data',pctpoints))

.

Answer 2

[Image Analyst]

"just colouring the points would be enough" <== One of the inputs to scatter is a vector of colors that you want each marker point to have.

help scatter

 scatter - Scatter plot

    Syntax
      Vector and Matrix Data
        scatter(x,y)
        scatter(x,y,sz)
        scatter(x,y,sz,c)
        scatter(___,"filled")
        scatter(___,mkr)

      Table Data
        scatter(tbl,xvar,yvar)
        scatter(tbl,xvar,yvar,"filled")

      Additional Options
        scatter(ax,___)
        scatter(___,Name,Value)
        s = scatter(___)

    Input Arguments
      x - x-coordinates
        scalar | vector | matrix
      y - y-coordinates
        scalar | vector | matrix
      sz - Marker size
        36 (default) | numeric scalar | row or column vector | matrix | []
      c - Marker color
        color name | RGB triplet | matrix of RGB triplets |
        vector of colormap indices
      mkr - Marker symbol
        "o" (default) | "+" | "*" | "." | "x" | ...
      "filled" - Option to fill interior of markers
        "filled"
      tbl - Source table
        table | timetable
      xvar - Table variables containing x-coordinates
        one or more table variable indices
      yvar - Table variables containing y-coordinates
        one or more table variable indices
      ax - Target axes
        Axes object | PolarAxes object | GeographicAxes object

    Name-Value Arguments
      MarkerEdgeColor - Marker outline color
        "flat" (default) | RGB triplet | hexadecimal color code | "r" |
        "g" | "b" | ...
      MarkerFaceColor - Marker fill color
        "none" (default) | "flat" | "auto" | RGB triplet |
        hexadecimal color code | "r" | "g" | "b" | ...
      LineWidth - Width of marker edge
        0.5 (default) | positive value
      ColorVariable - Table variable containing color data
        table variable index

    Output Arguments
      s - Scatter object
        Scatter object | array of Scatter objects

    Examples
      openExample('graphics/CreateScatterPlotExample')
      openExample('graphics/VaryCircleSizeExample')
      openExample('graphics/VaryCircleColorExample')
      openExample('graphics/ScatterColorPaletteExample')
      openExample('graphics/VaryCircleSizeandColorExample')
      openExample('graphics/SpecifyMarkerSymbolExample')
      openExample('graphics/SpecifyMarkerPropertiesExample')
      openExample('graphics/ScatterAlphaDataExample')
      openExample('graphics/ScatterTableExample')
      openExample('graphics/ScatterTableSizeColorExample')
      openExample('graphics/ScatterSpecifyAxes19bExample')
      openExample('graphics2/SetScatterObjectPropertiesExample')

    See also hold, plot, scatter3, bubblechart, swarmchart,
      Scatter Properties

    Introduced in MATLAB before R2006a
    Documentation for scatter
       doc scatter

    Other uses of scatter

       tall/scatter