# 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

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Please see editing help. Thanks. – Mr.Wizard Feb 15 '13 at 2:25
Could you post a sample data file with and without missing data? What are you using Paritition for? – s0rce Feb 15 '13 at 3:32
I am using the partition function to separate the long list of values into separate days. Eg: When I Import all the values for the light intensity I get a long list of values for 31 days. Therefore I will partition it into 31 parts to see the values for each day. – Raghav Malhotra Feb 15 '13 at 3:42
Partition is not the better way to do that. How to you import your txt? Do you have a sample txt? – Murta Feb 15 '13 at 4:18
@Murta The file can be found at link – Raghav Malhotra Feb 15 '13 at 4:25

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.}}

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Thank you! It works well! – Raghav Malhotra Feb 15 '13 at 10:18
Thank you for choosing my answer. I hope it helped. :) – Murta Feb 15 '13 at 10:22