# Delete points

Aim

To remove a sample (or some of the points of your sample) from your data set.

Deleting points means that they are set to missing.

important If you delete a point, you cannot recover the original coordinates, you can only interpolate it. If you delete an entire sample, the surface area is also lost. If you are not sure about the consequences of setting points to missing, save the edits first. You can always return to your original track data.

Procedure

1.Select the sample (or range) that contains the points you want to set to missing.

2.Do one or more of the following:

If your track contain only center-points, click the Set to missing button on the toolbar or press Ctrl+Del.

If your data also contains nose-point and tail-base, to set all points to missing, click the Set to missing button or press Ctrl+Del.

To set only nose-points to missing, click the Set nosepoint to missing button or press Ctrl+Shift+M.

To set only tail-base points to missing, click the Set tailbase to missing button or press Ctrl+M.

What “Set to missing” means

▪If you have set the whole selection to missing:

▪If you have set only the nose-points to missing:

▪If you have set only the tail-bases to missing:

Missing points are shown as linear interpolations between the non-missing points of their own type. However, their coordinates are not in the track data, and are not subject to analysis. For example, if sample n is missing, the distance moved between the two non-missing points n–1 and n+1 is given by the straight line connecting the two points of the same type (nose-point to nose-point, etc.).

▪In the Samples List, the points' X,Y coordinates are removed from the Samples List. If you set the sample to missing, the surface area is also removed. Missing values are indicated by "-".

▪If you set a nose-point to missing, the Head direction value for that sample is removed.