Add Keys For large data sets you will want to set keys
{"Image DocumentName": "Add Keys For large data sets you will want to set keys", "Image ImageDescription": "When data are keyed, they can be processed faster. A key is set to various columns in your data.table. When a column is associated with a key, it will be able to group the data by that column more rapidly. In our example, let s set participant id (ppt) and trialType as keys so we can group the data by these values more rapidly using the setkey command.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}