`preview`

Reads the first rows of a data file using import options.

Category: Language Fundamentals > Data Types

Syntax

T = preview(filename, opts)

Returns a table with the first rows that readtable(filename, opts) would read.

Description

preview is a cheap way to check that the import options select the right variables and types before reading a large file in full. Only a few lines are read, so it stays fast even for files with millions of rows.

Input arguments

filename: Name of a text or spreadsheet file.
opts: Import options object, for example from detectImportOptions.

Output arguments

T: Table with at most eight rows.

Example

fid = fopen('scores.csv', 'w');
fprintf(fid, 'id,score\n1,2.5\n2,3.5\n3,4.5\n');
fclose(fid);
opts = detectImportOptions('scores.csv');
preview('scores.csv', opts)

Output

ans = 3×2 table

    id    score
    __    _____

    1      2.5 
    2      3.5 
    3      4.5

Notes

In MatLivre the import options argument is required.

preview