Replaced histogram with a line indicator over a zero line.
NOTE: the FRED:FEDFUNDS rate is only updated monthly, so while this indicator is useful for looking back, it will lag real time rate changes by a couple of weeks. For faster data, use the IORB weighted version of this indicator instead. I will link it in the comments below.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.