these guesses. Ideally, the column types would be completely obvious from the first non-header row and we could use <code>guess_max = 1</code>. That would be very efficient! But the situation is rarely so clear-cut.</p>
<p>By default, readr consults 1000 rows when type-guessing, i.e. <code>guess_max = 1000</code>. Note that readr never consults rows that won’t be part of the import, so the actual default is <code>guess_max = min(1000, n_max)</code>.</p>
<p>Sometimes you want to convey “use all of the d