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Import Block of Mixed Data from Text File into Table or Cell Array

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This example reads a block of mixed text and numeric data from a text file, and then imports the block of data into a table or a cell array.

Data File Overview

The sample filebigfile.txtcontains commented lines beginning with ##. The data is arranged in five columns: The first column contains text indicating timestamps. The second, third, and fourth columns contain numeric data indicating temperature, humidity and wind speed. The last column contains descriptive text. Display the contents of the filebigfile.txt.

type('bigfile.txt')
## A ID = 02476 ## YKZ Timestamp Temp Humidity Wind Weather 06-Sep-2013 01:00:00 6.6 89 4 clear 06-Sep-2013 05:00:00 5.9 95 1 clear 06-Sep-2013 09:00:00 15.6 51 5 mainly clear 06-Sep-2013 13:00:00 19.6 37 10 mainly clear 06-Sep-2013 17:00:00 22.4 41 9 mostly cloudy 06-Sep-2013 21:00:00 17.3 67 7 mainly clear ## B ID = 02477 ## YVR Timestamp Temp Humidity Wind Weather 09-Sep-2013 01:00:00 15.2 91 8 clear 09-Sep-2013 05:00:00 19.1 94 7 n/a 09-Sep-2013 09:00:00 18.5 94 4 fog 09-Sep-2013 13:00:00 20.1 81 15 mainly clear 09-Sep-2013 17:00:00 20.1 77 17 n/a 09-Sep-2013 18:00:00 20.0 75 17 n/a 09-Sep-2013 21:00:00 16.8 90 25 mainly clear ## C ID = 02478 ## YYZ Timestamp Temp Humidity Wind Weather

Import Block of Data as Table

To import the data as a table, usereadtablewith import options.

Create an import options object for the file using thedetectImportOptionsfunction. Specify the location of the data using theDataLines财产。For example, lines3through8contain the first block of data. Optionally, you can specify the names of the variables using theVariableNames财产。最后导入第一个数据块usingreadtablewith theoptsobject.

opts = detectImportOptions('bigfile.txt'); opts.DataLines = [3 8]; opts.VariableNames = {'Timestamp','Temp',...'Humidity','Wind','Weather'}; T_first = readtable('bigfile.txt',opts)
T_first=6×5 tableTimestamp Temp Humidity Wind Weather ____________________ ____ ________ ____ _________________ 06-Sep-2013 01:00:00 6.6 89 4 {'clear' } 06-Sep-2013 05:00:00 5.9 95 1 {'clear' } 06-Sep-2013 09:00:00 15.6 51 5 {'mainly clear' } 06-Sep-2013 13:00:00 19.6 37 10 {'mainly clear' } 06-Sep-2013 17:00:00 22.4 41 9 {'mostly cloudy'} 06-Sep-2013 21:00:00 17.3 67 7 {'mainly clear' }

Read the second block by updating theDataLinesproperty to the location of the second block.

opts.DataLines = [11 17]; T_second = readtable('bigfile.txt',opts)
T_second=7×5 tableTimestamp Temp Humidity Wind Weather ____________________ ____ ________ ____ ________________ 09-Sep-2013 01:00:00 15.2 91 8 {'clear' } 09-Sep-2013 05:00:00 19.1 94 7 {'n/a' } 09-Sep-2013 09:00:00 18.5 94 4 {'fog' } 09-Sep-2013 13:00:00 20.1 81 15 {'mainly clear'} 09-Sep-2013 17:00:00 20.1 77 17 {'n/a' } 09-Sep-2013 18:00:00 20 75 17 {'n/a' } 09-Sep-2013 21:00:00 16.8 90 25 {'mainly clear'}

Import Block of Data as Cell Array

You can import the data as a cell array using thereadcellfunction withdetectImportOptions, or by using thetextscanfunction. First import the block of data using thereadcellfunction and then perform the same import by usingtextscan.

To perform the import using the readcell function, create an import options object for the file using thedetectImportOptionsfunction. Specify the location of the data using theDataLines财产。Then, perform the import operation using thereadcellfunction and import options objectopts.

opts = detectImportOptions('bigfile.txt'); opts.DataLines = [3 8];% fist block of dataC = readcell('bigfile.txt',opts)
C=6×5 cell array{[06-Sep-2013 01:00:00]} {[ 6.6000]} {[89]} {[ 4]} {'clear' } {[06-Sep-2013 05:00:00]} {[ 5.9000]} {[95]} {[ 1]} {'clear' } {[06-Sep-2013 09:00:00]} {[15.6000]} {[51]} {[ 5]} {'mainly clear' } {[06-Sep-2013 13:00:00]} {[19.6000]} {[37]} {[10]} {'mainly clear' } {[06-Sep-2013 17:00:00]} {[22.4000]} {[41]} {[ 9]} {'mostly cloudy'} {[06-Sep-2013 21:00:00]} {[17.3000]} {[67]} {[ 7]} {'mainly clear' }

To perform the import using thetextscanfunction, specify the size of block usingNand the format of the data fields usingformatSpec. For example, use'%s'for text variables,'%D'for date and time variables, or'%c'for categorical variables. Set the'DateLocale'name-value argument to'en_US'to ensure that the names of the months are interpreted in English. Usefopento open the file. The function then returns a file identifier,fileID. Next, read from the file by using thetextscanfunction.

N = 6; formatSpec ='%D %f %f %f %c'; fileID = fopen('bigfile.txt');

Read the first block and display the contents of the variableHumidity.

C_first = textscan(fileID,formatSpec,N,'CommentStyle','##','Delimiter','\t','DateLocale','en_US')
C_first=1×5 cell array{6×1 datetime} {6×1 double} {6×1 double} {6×1 double} {6×1 char}
C_first{3}
ans =6×189 NaN 95 NaN 51 NaN

Update the block size N, and read the second block. Display the contents of the fifth variableWeather.

N = 7; C_second = textscan(fileID,formatSpec,N,'CommentStyle','##','Delimiter','\t','DateLocale','en_US')
C_second=1×5 cell array{7×1 datetime} {7×1 double} {7×1 double} {7×1 double} {7×1 char}
C_second{5}
ans =7×1 char array'm' '↵' 'm' '↵' 'm' '↵' 'c'

Close the file.

fclose(fileID);

See Also

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