Grid a plot with diagonal lines

I would like to plot a diagonal grid where there are three or four lines of positive slope=1 like in the figure attached.

I don't see an equivalent of the command, "grid" that efficiently creates a horizontal–vertical grid (maybe someone knows of one?). So instead I'm trying to do it this way, where I avoid having to hard-code anything because I have many plots and will have to update them regularly.

xL = get(gca, 'XLim');
plot(xL,xL);

This gives me one line that goes through the origin, is positive, and has slope=1. However--silly question, I know--I can't figure out how to get additional lines that parallel the line. If anyone has any hints on this, I'd be grateful.

Answer 1

[Mischa Kim]

There are a couple of things you could do. E.g.

x = -5:1:5; N = numel(x);
X = ones(N,1)*x;
Y = X + X';
plot(X',Y');
grid

[Srh Fwl]

Thank you, Mischa; exactly what I need.

Answer 2

[Adam Danz]

ConstantLine objects extend to the axis limits even when the limits change but as of r2020b, ConstantLine objects can only be vertical (xline) or horizontal (yline).

To create a diagonal constant line that extend to the axis limits even when the limits are changed, you can apply a listener that updates the line coordinates as needed.

% Set up demo
clf
ax = axes;
hold(ax, 'on')
grid(ax, 'on')

% Add reference lines using refline([slope, y-intercept])
% Alternatively, you can use r=plot() or r=line() where each line is defined
% by two and only two coordinates (x0,y0),(x1,y1).
r(1) = refline(ax, [1,-.5]);
r(2) = refline(ax, [1, 0]);
r(3) = refline(ax, [1, .5]);
set(r, {'Color'}, {'r';'b';'g'}, 'LineWidth', 2)

% Add listener to update the reference lines when the
% axis limits are changed
addlistener(ax, {'XLim', 'YLim','XLimMode','YLimMode'}, 'PostSet', @(~,~)reflineListenerFcn(ax,r)); 


function reflineListenerFcn(ax,r)
% Responds to changes in xlim,ylim in axes 'ax'. Updates the 
% xdata and ydata for reference lines 'r'.  
r(~isvalid(r)) = []; 
xdata = reshape([r.XData],2,[]);
ydata = reshape([r.YData],2,[]);
slope = diff(ydata,[],1) ./ diff(xdata,[],1);
yint = ydata(1,:) - slope.*xdata(1,:);
xl = xlim(ax); 
yl = ylim(ax); 
newY = slope'.*xl + yint'; 
newX = (newY-yint')./slope';
set(r,{'XData'},mat2cell(newX,ones(size(newX,1),1),2),...
    {'YData'},mat2cell(newY,ones(size(newY,1),1),2))
xlim(ax,xl)
ylim(ax,yl)
end