subsetting

Hello, I have a presumably easy question for you, but I am a real newbie in statistics, so please be patient. I have a data set containing N values that more or less follows a normal distribution. I need to select N/10 values among them, creating a subset with the same distribution. How can I...

Hi, I am trying to create a subset of data of “high intermediate risk” group of entries as defined by a criteria based on age and number of risk factors. It is: Age over 70 plus at least 1 risk factor Age 50-70 plus at least 2 risk factors Age under 50 plus all three risk factors The...

Hi, I have a matrix x with 97 rows and used the function sample like this : rownumbers=sample(1:97,size=70) data1=x[rownumbers,] I'm having trouble to get the rows which are not inside data1 into another matrix. Does anyone have an idea? greets, Taibo