import - Importing data sets from plain-text files and performing operations on them

I am working with a lot of daily weather files in the txt format. I need to calculate a daily quantity from each of them, e.g., daily light intensity, which involves a simple summation of the light intensity column in Excel. As I am working with over three years of data, it is not possible to do this manually.

How can I automate this in Mathematica? Currently I import all the files using the following method. (Example shown is for Jan 1 to Jan 31)

filenames = FileNames[];  
TestList = Flatten[Table[Files[[j, i]], {j, 1, 31}, {i, 2, 1437}], 1];  
LightIntensity = TestList[[1 ;;, 5]];  
DailyLightIntensity = Partition[LightIntensity, 1436];  

DailySummation = Table[Total[DailyLightIntensity[[i]]],  {i, 1, 31}]

The method above only works assuming all the txt files contain rows from 2 to 1436, so I can use Partition, but I also need to handle cases with missing data.

I want to automate this process with Mathematica , import each txt file separately, perform the necessary calculations, and store the answer. How can this be done?

The naming convention of the txt is given below:

[112] 2012-01-01
[112] 2012-01-02
[112] 2012-01-03
[112] 2012-01-04

...
[112] 2012-12-31

Answer

This can be a starting point:

data=Rest@Import["http://dl.dropbox.com/u/10371498/SampleFile.txt", "TSV"];
{First@StringSplit[data[[1, 1]]],Total[data[[All,2]]]}

So you get:

{"1/1/12", 308439.}

For many files and for filter data you can create a function like:

resumeFile[fileName_]:=Module[{data},
    data=Rest@Import[fileName, "TSV"];
    data=Select[data, #[[2]] > 50 &];
    {First@StringSplit[data[[1, 1]]],Total[data[[All,2]]]}
]

And make it operate in each txt like:

SetDirectory@"C:/txtPath"

files=FileNames["[112]*.txt"]
resumeFile/@files

You should get a list:

{{"1/2/12", 308439.},{"1/2/12", 208389.}, ... , {"1/3/12", 508439.}}