5. AVERAGING

Choose a set of images (.obj) you want to include in the average.

SINGLE AVERAGE

For a small number of images:

1. Open the first warped file (or any other) from the folder.

2. If the 3D images have not been normalised to a standard orientation, select Statistics->Auto procrustes normalise, this will minimise the differences due to rotation, translation and scale before averaging.

3. Select "Add to Average..." from the "Statistics" menu. Morphanalyser will promt you to select another image (.obj) to add to the average.

4. Select the next warped image from the folder and the image on the screen should be updated.

5. To add further warped images continue "Add to Average..." until all the warped files have been included.

6. Save the resulting average image by selecting "Save Average" from the "File" menu and save it as an average (.avg) file. (note: using "Save" from the "File" menu will save image as an object file (.obj) and some average information will be lost for statistical shape comparison)

BATCH AVERAGE

For a larger number of images:

1. Create a notepad file (.txt)

2. If the 3D images have not been normalised to a standard orientation, select "Statistics->Auto procrustes normalise", this will minimise the differences due to rotation, translation and scale before averaging. For best results all faces should be procrustes normalised to the average before averaging. As the average is initially unknown an iterative process can be used that aligns faces to the current estimate of the average and iterates afew times. Tick "Statistics->Iterate average" to achieve this.

3. Write a list of the warped image files you want to include in the average by adding " " around each filename if it starts

with a number. E.g.

"1790_1733.obj"

"1790_2051.obj"

"1790_2053.obj"

"1790_2068.obj"

4. Save the text file in the same folder where the warped images are located (note: it is possible to have the .txt file in a

superordinate folder - for that consult the MorphAnalyser "Help Menu").

5. Open one of the warped image files from the folder.

6. To create an average select "Average List" from the "Statistics" menu:

Morphanalyser will promt you to select a text file (.txt).

7. Select your created notepad file and the average image from the set should be displayed.

8. Select "Save Average" from the "File" menu and save it as an average (.avg) file.

(note: using "Save" from the "File" menu will save image as an object file (.obj) and the point distribution information will be lost)