Reading a text file containing strings.

I have a data recorded from a sensor every day which is listed below:

34312810010110000000000000000000000000000000000000000000000000000000000000000 34312810010210000000000000000000000000000000000000000000000000000000000000000 34312810010310000000000000000000000000000000000000000000000000000000000000000 34312810010410000000000000000000000000000000000000000000000000000000000000000 34312810010510000000000000000000000000000000000000000000000000000000000000000 34312810010610000000000000000000000000000000000000000000000000000000000000000 34312810010710000000000000000000000000000000000000000000000000000000000000000 34312810010810000000000000000000000000000000000000000000000000000000000000000 34312810010910000000000000000000000000000000000000000000000000000000000000000 34312810011010000000000000000000000000000000000000000000000000000000000000000 34312810011110000000000000000000000000000000000000000000000000000000000000000

I have written a code for interpreting the data as follows:

str = '34312810010110000000000000000000000000000000000000000000000000000000000000000'

D1=str(1) % Element Indicator

D2=str(2:6) % Index number of the station

D3=str(7:8) % Year

D4=str(9:10) % Month

D5=str(11:12) % Date

D6=str(13) % Record Number

and so on

D7

:

:

etc as upto the end of the first line and later I convert these strings to numbers using strl2num.

I am able to process the data for one line with this code, how to do the same process repeadedly for 'n' number of lines keeping the whole data in a text file.

Thanks in advance.

Lakshmi.

Answer 1

[Star Strider]

It would have been appropriate to include the file you want to read. Lacking that, I created my own version (‘Dhanalakshmi M 20210322.txt’, attached) to test this.

The Code —

opts = detectImportOptions('Dhanalakshmi M 20210322.txt');
VarNames = {'ElementIndicator','StationIndexNumber','Year','Month','Day','RecordNr','AndSoOn'};
VarWidths = [1, 6, 2, 2, 2, 1, 77-14];
VarTypes = {'int64','double','int64','int64','int64','int64','int64'};
opts = fixedWidthImportOptions('NumVariables',7, 'VariableNames',VarNames, 'VariableWidths',VarWidths, 'VariableTypes',VarTypes);

Mread = readtable('Dhanalakshmi M 20210322.txt', opts);
Mread.StationIndexNumber = Mread.StationIndexNumber * 1E+5;

The Result —

Mread =

  11×7 table

    ElementIndicator    StationIndexNumber    Year    Month    Day    RecordNr    AndSoOn
    ________________    __________________    ____    _____    ___    ________    _______

           3                  43128            10       1       1        1           0   
           3                  43128            10       1       2        1           0   
           3                  43128            10       1       3        1           0   
           3                  43128            10       1       4        1           0   
           3                  43128            10       1       5        1           0   
           3                  43128            10       1       6        1           0   
           3                  43128            10       1       7        1           0   
           3                  43128            10       1       8        1           0   
           3                  43128            10       1       9        1           0   
           3                  43128            10       1      10        1           0   
           3                  43128            10       1      11        1           0   

For some reason, ‘StationIndexNumber’ was imported with a leading decimal point. I solved that by simply multiplying it by . Perhaps not the most elegant solution, however it has the advantage of producing the correct result.

Make appropriate changes to get the result you want.

EDIT — Corrected typographical errors.

[Dhanalakshmi M]

Sir,

I am attaching a sample file that is recorded by the sensor. The data from the sensor is continous for different parameters, further the data is not always zero, on most of the days there will be some values recorded for different parameters. I am attaching a sample file for your kind reference. I have written a code that works fine for one line (or day) but I what this to be done for all the lines (days). I am a student doing a project work, and I don't know how to put this in a loop, your help in this regards would be of great help to me. Further is it necessary to convert the data to exponential form before processing.

Further I am getting this error while running your code.

Undefined function 'detectImportOptions' for input arguments of type 'char'.

[Star Strider]

This is the best I can do:

filename = 'Hyd_Sample_1.txt';
opts = detectImportOptions(filename);
VarNames = {'ElementIndicator','StationIndexNumber','Year','Month','Day','RecordNr','Field_07','Field_08','Field_09','Field_10'};
VarWidths = [1, 6, 2, 2, 2, 1, 63, 15, 48, 2];
VarTypes = {'int64','int64','int64','int64','int64','int64','int64','int64','int64','int64'};
opts = fixedWidthImportOptions('NumVariables',10, 'VariableNames',VarNames, 'VariableWidths',VarWidths, 'VariableTypes',VarTypes);

SensorData = readtable(filename, opts);

with:

First_10_Rows = SensorData(1:10,:)

producing:

First_10_Rows =

  10×10 table

    ElementIndicator    StationIndexNumber    Year    Month    Day    RecordNr    Field_07       Field_08        Field_09    Field_10
    ________________    __________________    ____    _____    ___    ________    ________    _______________    ________    ________

           3                  431281           0       10      11        0           0        203431281001012       0           20   
           3                  431281           0       10      21        0           0        203431281001022       0           20   
           3                  431281           0       10      31        0           0        203431281001032       0           20   
           3                  431281           0       10      41        0           0        203431281001042       0           20   
           3                  431281           0       10      51        0           0        203431281001052       0           20   
           3                  431281           0       10      61        0           0        203431281001062       0           20   
           3                  431281           0       10      71        0           0        203431281001072       0           20   
           3                  431281           0       10      81        0           0        203431281001082       0           20   
           3                  431281           0       10      91        0           0        203431281001092       0           20   
           3                  431281           0       11       1        0           0        203431281001102       0           20   

‘Further is it necessary to convert the data to exponential form before processing.’

I have no idea what that means, or how to interpret it. I read these all as int64 numbers to be certain that they have the appropriate precision, and imported all the digits. (They do.) Change them as necessary to produce the variable types (the ‘VarTypes’ vector in my code, see the VariableTypes section of the fixedWidthImportOptions documentation) that you want. You can also change any of them them to 'double' by changing the variable type I assigned to them, or you can change them after my code reads them with the appropriate functions, for example double. There is no ‘exponential’ variable type in MATLAB.

See the documentation on fixedWidthImportOptions for more information.

.

[Dhanalakshmi M]

Sir, i am getting the following error while running the code.

Wrong number of arguments.

SensorData = readtable(filename, opts);

[Rik]

When posting an error message, make sure to include the entire message (i.e. all red text).

[Dhanalakshmi M]

Sir,

The error is given below: Further I am using R2014a version.

Error using table.readFromFile (line 8)

Wrong number of arguments.

Error in readtable (line 118)

t = table.readFromFile(filename,varargin);

Error in Ram4 (line 18)

SensorData = readtable(filename, opts);

[Star Strider]

My code as I posted it ran for me without error in R2021a.

The readtable function was introduced in R2013b, however detectImportOptions was introduced in R2016b and fixedWidthImportOptions (function) in R2018b.

It will be necessary to upgrade to at least R2018b (and preferably to R2021a) to run my code. I no longer have access to R2014b (or even its documentation), so I have no idea currently how to work around that limitation to parse your file.

I will see if I can come up with something using the fileread function, although it will not be as efficient as the code I posted.

[Dhanalakshmi M]

Sir, Thanks for your kind reply. I have altered other lines as per the R2014a version, but I am getting error on this line only SensorData = readtable(filename, opts); I am trying to solve this error, it is giving wrong number of arguments. Thanks once again for your help.