How to draw a "xline" with a given height for the line and a given vertical position for the text?

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Sim 2022-3-11

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评论： Sim 2022-3-11

How to draw a xline with a given height for the line and a given vertical position for the text?

In other words, I need a shorter xline and I want to decide exactly how short that line will be.

Also, I would like to customise more the vertical position of the text, i.e. putting it a bit higher or a bit lower than what given by 'LabelVerticalAlignment'.

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Answer 1

Star Strider 2022-3-11

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The xline function by default goes to the limits if the y-axis. The label only has limited options for positioning.

It will likely be easier to create a single vertical line and attach a text object to it:

x = 1:0.1:10;

y = sin(2*pi*x/5);

figure

plot(x, y)

[xl,xt] = xlin(7,'Message', 0.1, 0.8, 0.25);

grid

function [hl,ht] = xlin(x,txt,ylo,yhi,ytxt)

% Documentation:

% x = x-Position

% txt = Text String

% ylo = Low y-Value (Start)

% yhi = High y-Value (End)

% ytxt = Text Starting Position

hold on

hl = plot([x x],[ylo yhi],'DisplayName',txt, 'LineWidth',1);

ht = text(x,ytxt, txt, 'Horiz','left', 'Vert','top', 'Rotation',90);

hold off

end

Returning the ‘hl’ and ‘ht’ handles permits easily changing certain attributes of the line and text objects without changing the function.

.

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Sim 2022-3-11

Thanks a lot, exactly what I needed!!! :)

Star Strider 2022-3-11

As always, my pleasure!

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Answer 2

Voss 2022-3-11

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Here's how you can specify the Vertical and Horizontal Alignment of the xline's label:

warning off all

figure();

xline(1,'_','Line at x = 1','LabelVerticalAlignment','top');

xline(2,'_','Line at x = 2','LabelVerticalAlignment','bottom');

xline(3,'-','Line at x = 3','LabelVerticalAlignment','middle');

xlim([0 4]);

figure();

xline(1,'_','Line at x = 1','LabelHorizontalAlignment','left');

xline(2,'_','Line at x = 2','LabelHorizontalAlignment','right');

xline(3,'_','Line at x = 3','LabelHorizontalAlignment','center');

xlim([0 4]);

If you don't want the xline itself to span the y-limits of the axes, i.e., have an xline of a given height, and/or have more control over where the label is, then you're better off creating a regular line (not an xline) and a text label separately:

figure();

line([1 1],[0 4],'Color','k');

text(1,1.5,'Line at x = 1','Rotation',90,'VerticalAlignment','bottom','HorizontalAlignment','center');

ylim([0 6]);

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Voss 2022-3-11

编辑：Voss 2022-3-11

You're welcome!

Note that it is more efficient to use the low-level function line() than the high-level function plot(), and that plot() can potentially do unwanted things to your axes (or objects in it) that line() will not do. Therefore, I think it is better to use line() for this purpose.

Sim 2022-3-11

Ah ok, I did not know it....... Can I accept both answers?? I would like to... :-)

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Answer 3

Walid 2022-3-11

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Please check ConstantLine Properties (frome MATLAB R2021a):

you must use: xline(5,'LabelHorizontalAlignment',''left'') and likewise LabelVerticalAlignment for top, middle or button of the xline.

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Sim 2022-3-11

编辑：Sim 2022-3-11

Thanks @Walid... I am already using those properties.... But, I need to customise them with precise/given heights/positions (not just the usual 'left','right','up','down',...)

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