Thresholds · Sentiment Analysis for PHP

The label is decided by comparing the compound score against a threshold. The scores themselves never change; only the label does.

Condition	Label
`compound > 0` and `compound >= threshold`	`Label::Positive`
`compound < 0` and `compound <= -threshold`	`Label::Negative`
anything else	`Label::Neutral`

So with the default threshold of 0.05, the neutral band is the open interval between -0.05 and +0.05: anything from -0.0499 to 0.0499 is neutral. A compound of exactly 0.05 is positive and -0.05 is negative.

Change the threshold

Pass it to the constructor or use withThreshold():

use Risan\Sentiment\Analyzer;

$analyzer = new Analyzer(threshold: 0.1);

$strict = $analyzer->withThreshold(0.4);

A wider neutral band means fewer texts get a positive or negative label. It suits cases where a wrong confident label is costly, such as auto-replying to unhappy customers. A narrower band catches weaker signals, at the price of more false alarms.

Threshold	Neutral band	Use when
`0`	only `compound = 0`	you want a label for every text with any signal
`0.05` (default)	-0.05 to 0.05	general use, the VADER recommendation
`0.2` to `0.4`	wider	you only want clearly polarized texts

Limits

The threshold must be at least 0 and lower than 1. Anything else throws an InvalidArgumentException:

(new Analyzer())->withThreshold(1.0);  // InvalidArgumentException
(new Analyzer())->withThreshold(-0.1); // InvalidArgumentException

A text whose compound is exactly 0 is always neutral, even at threshold 0.

Skip the label

If you already have your own cutoffs, ignore the label and use the numbers:

$result = $analyzer->analyze($text);

if ($result->compound >= 0.6) {
    // very happy
}