Use this:
str2double(vertcat(lat{:}))
How this works:
lat{:}
gives you a comma-separated list of the cell contents. Each cell content is in turn a single-column cell-array of strings (I assume).
vertcat
concatenates all those single-column cell-arrays of strings into one single-column cell-array of strings.
str2double
converts each string into a double
number and packs all those numbers into a column vector.
Example:
lat{1,1} = {
'40.400959'
'40.695078'
'40.969112'
'41.264171'
'41.400968'
'41.517772'
'41.530011'
'41.550005'
'41.583183'
'41.603159'};
lat{1,2} = {
'38.082155'
'38.176278'
'38.529631'
'38.612034'
'38.700632'};
gives
ans =
40.4010
40.6951
40.9691
41.2642
41.4010
41.5178
41.5300
41.5500
41.5832
41.6032
38.0822
38.1763
38.5296
38.6120
38.7006