Why does DLMREAD return a column vector when I used DLMWRITE to create an ASCII-delimited file with a row vector in MATLAB 7.1 (R14SP3)?

I used DLMWRITE to write a large (> 100,000 elements) row vector to a tab-delimited ASCII file. When I read it back into MATLAB with DLMREAD, it is read as a column vector. This also happens when using TEXTSCAN.

Answer 1

[MathWorks Support Team]

This is the expected behavior in MATLAB 7.1 (R14SP3). DLMREAD calls TEXTSCAN, which has a current limit of 100,000. Thus, a single line with more than 100,000 fields is read in as a column, instead of a row by TEXTSCAN. This allows TEXTSCAN to use a single cell holding an array as opposed to a large cell array, thereby providing improvements in memory and hence speed.

To work around this issue, use the data Import Wizard or the LOAD command with the following syntax:

load -ascii filename.dat