[R] Help on Aggregation

Dear All, 1.I have been trying to aggregate my data but I have not been getting it correctly. In the data I want to convert hourly data into daily averages. Here is a sample of the data: Neph_no Date Time Temp_C Pressure_kPa RH 9 2014/03/28 10:00:00 38.4 95.9 29.7 9 2014/03/28 11:00:00 37.8

[R] Packages couldn't load

Dear All, I have been trying to install Xlsx package in R but i have been getting this error after the installation. Please can anyone help? > any(grepl("xlsx",installed.packages())) [1] TRUE > library("xlsx") Loading required package: rJava Error: package or namespace load failed for ‘rJava’: .