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ginput

Identify axes coordinates

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Syntax

[x,y] = ginput(n)
[x,y] = ginput
[x,y,button] = ginput(___)

Description

[x,y] = ginput(n) allows you to identify the coordinates of n points within Cartesian, polar, or geographic axes. To choose a point, move your cursor to the desired location and press either a mouse button or a key on the keyboard. Press the Return key to stop before all n points are selected. MATLAB® returns the coordinates of your selected points. If there are no axes, calling ginput creates a Cartesian axes object.

example

[x,y] = ginput allows you to select an unlimited number of points until you press the Return key.

example

[x,y,button] = ginput(___) also returns the mouse button or key on the keyboard used to select each point.

example

Examples

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Identify four points in a set of axes using ginput. To select each point, move the cursor to your desired location and press a mouse button or key.

[x,y] = ginput(4)

Cartesian axes with cursor for selecting a point

x =

    0.3699
    0.4425
    0.5450
    0.6130


y =

    0.6690
    0.5605
    0.4719
    0.6025

Plot the identified points.

plot(x,y);

Cartesian axes with plot of four identified points

Identify five coordinates in a set of axes using ginput. To select each point, move the cursor to your desired location and press a mouse button, lowercase letter, uppercase letter, number, or the space bar. Return the mouse buttons or ASCII numbers of the keys used to select each point.

[x,y,button] = ginput(5);
button

button =

     3
   104
    32
    51
    82

In this case, the coordinates were identified using the right mouse button (3), the lowercase letter h (104), the space bar (32), the number 3 (51), and the uppercase letter R (82).

Create geographic axes and identify the latitude and longitude coordinates of four points. Then, plot the points that you identify.

geoaxes
[lat,lon] = ginput(4);

Geographic axes with cursor for selecting a point

Use the hold on command and the geolimits function to maintain the map limits. Plot the identified points.

hold on
geolimits('manual')
geoscatter(lat,lon,'filled','b')

Geographic axes with blue circles identifying four points

Input Arguments

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Number of points to identify, specified as a positive integer.

Output Arguments

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First components of the identified coordinates, returned as a scalar or column vector.

  • For Cartesian axes, the values are x-coordinates.

  • For polar axes, the values are theta angles. The theta angles are in the range [tmin, tmin+2*pi], where tmin is the first value of the ThetaLim vector of the polar axes. The angles are measured from the location of the zero angle in the direction specified by the ThetaDir property. The location of the zero angle is specified by the ThetaZeroLocation property.

  • For geographic axes, the values are latitudes. Positive values correspond to north and negative values correspond to south.

If you choose points outside the axes limits, the values are relative to the origin for Cartesian and geographic axes. For polar axes, the values are relative to the ThetaZeroLocation.

Second components of the identified coordinates, returned as a scalar or column vector.

  • For Cartesian axes , the values are y-coordinates.

  • For polar axes, the values are radii. Each radius value is greater than or equal to rmin, where rmin is the first value in the RLim vector of the polar axes.

  • For geographic axes, the values are longitudes. Positive values correspond to locations east of the origin and negative values correspond to locations west of the origin.

If you choose points outside the axes limits, values are still returned relative to the axes origin.

Keys or mouse buttons used to identify points, returned as a scalar or column vector. Mouse buttons are indicated by 1 for the left button, 2 for the middle, and 3 for the right. Double-clicks are indicated by two values. The first value is 1 for the left mouse button, 2 for the middle, and 3 for the right. The second value is 1.

Keys on the keyboard are indicated by their corresponding ASCII numbers. Taps on a screen are indicated by 1.

For example, call ginput, click using the middle mouse button, double-click using the right mouse button, and then press Enter. The output button is a vector containing 2, 3, and 1.

[~,~,button] = ginput
button =

     2
     3
     1

Version History

Introduced before R2006a

See Also

Functions