The mean value for a first column in a matrix

i have 6x3 matrix and i want to calculate mean value of first column without  the second and  third one 

[Umut Oskay]

also i know x= mean(nameofmatrix, 1) it shows all columns seperately. i need just first one

[Peng Li]

mean(nameofmatrix(:, 1));

[Umut Oskay]

thanks a lot but can you explain the function of : in this case

[Peng Li]

colon index is one of the most useful operator in MATLAB. i recommend you check the reference link for colon index.

https://www.mathworks.com/help/matlab/ref/colon.html

besically, a(:, n) means the nth column of matrix a.

[Umut Oskay]

thanks a lot