Scatter plot with different color for points above the linear fit line

Hi,

In my regression analysis I am geting two different lobes of data. I want to get different color for points above the regression line in the scatter plot and know their positions.

Thanks!

Answer 1

[Tommy]

Here's a simple example using a linear regression, hopefully you find it helpful:

% random data
X = rand(100,1);
Y = 0.5*X + rand(100,1);

% linear regression
b = [ones(numel(X),1), X]\Y;
Yfit = b(2)*X + b(1); % Y(i) and Yfit(i) are located at same x value

% compare corresponding points in y direction
idx = Y > Yfit; % idx(i) tells whether Y(i) is above Yfit(i)

% plot
scatter(X(idx),Y(idx),'r');
hold on;
scatter(X(~idx),Y(~idx),'b');
plot(X,Yfit,'k');