# HydroGeoSphere/Selecting Segments

We can use the following instructions to alter the set of chosen segments.

## Clear chosen segmentsEdit

All segments in the domain are flagged as *not* chosen. This is recommended if you are unsure of which segments are chosen due to previously issued instructions.

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## Choose segments allEdit

All segments in the domain will be chosen. This is useful if you wish to assign a property to all segments in the grid.

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## Choose segments lineEdit

**x1, y1, z1***xyz*-coordinates of the first end point of the line.**x2, y2, z2***xyz*-coordinates of the second end point of the line.

Segments which fall on or close to the line are chosen. The routine finds the two nodes closest to the end points of the line and then finds the group of connected line segments which form the shortest path between the two nodes.

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## Choose segments polylineEdit

**npts**The number of points defining the polyline, which should be entered in order from one end of the polyline to the other. Read the following**npts**times:

- (a)
**x1, y1, z1***xyz*-coordinates of a point on the polyline.

- (a)

Segments which fall on or close to the polyline are chosen. The routine proceeds along the polyline, considering two points at a time, finds the two nodes closest to the two current points and then finds the group of connected line segments which form the shortest path between the two nodes.

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