Why does the IMPORTDATA function read in my file incompletely in MATLAB 7.6 (R2008a) and later?

I am reading in a file, which contains rows with both text data and numeric data, using IMPORTDATA. The IMPORTDATA function stops reading in data from the file when it encounters text data after numeric data.

Answer 1

[MathWorks Support Team]

This is an expected behavior of the IMPORTDATA function.

The IMPORTDATA function is designed and intended to read a "rectangular" block of numeric data, possibly bordered by rows and/or columns of headers.

For your file, the IMPORTDATA function would detect the "data rectangle" as the block of numeric data that follows the initial lines of text data. These initial lines of text data would be read into the 'textdata' field of the output structure and the numeric data would be read into the 'data' field of the output structure. Any text data that follows the numeric data will be ignored.

For example, let 'Example_file.txt' contain both text and numeric data as follows:

 Header

 1

 Day1  Day2  Day3  Day4  Day5  Day6  Day7

 95.01 76.21 61.54 40.57  5.79 20.28  1.53

 23.11 45.65 79.19 93.55 35.29 19.87 74.68

 60.68  1.85 92.18 91.69 81.32 60.38 44.51

 48.60 82.14 73.82 41.03  0.99 27.22 93.18

 89.13 44.47 17.63 89.36 13.89 19.88 46.60

The command,

M = importdata('Example_file.txt');

will read in just the string 'Header' into the 'textdata' field of M and the number '1' into the 'data' field of M, ignoring the remaining data.

 M = 

           data: 1

       textdata: {'Header'}

     rowheaders: {'Header'}

To read in the 5x7 block of data into the 'data' field, execute the following command instead:

M = importdata('Example_file.txt',' ',3);

The third argument '3' specified for the IMPORTDATA command indicates that the first 3 lines of the file will be treated as header text data. Hence, the 5x7 block of data will be read into the 'data' field of M.

 M = 

           data: [5x7 double]

       textdata: {3x7 cell}

     colheaders: {'Day1'  'Day2'  'Day3'  'Day4'  'Day5'  'Day6'  'Day7'}