Exercises : Data Manipulation

We will use an online dataset http://rcursus.dairyconsult.nl/lime.prn
Read the dataset into an object called lime
Use the function is.na() to check if the column pH contains any NA values ?
Make a subset lime.sub that only contains pH values above 5.90.
Compare the sizes of lime and lime.sub
In lime, change the values in the column type:
- AL should become Agricultural
- GL should become Granular
Make a subset lime.sub2 from lime with only the columns type and pH and only rows where rate is smaller than 2. What are the number of rows and columns in lime.sub2 ?

Order lime on the column pH and check the result.
Save your the resulting object as a lime.csv document.
Save your scripts as a .R file.
(if time permits : calculate the mean pH for each level of rate in lime and in lime.sub).

Exercises : Basic Statistics

create a vector r1 with 10 random numbers from a normal distribution with mean 1 and s.d. 1
create a vector r0 with 10 random numbers from a normal distribution with mean 0 and s.d. 1
Perform a t-test for difference of means of r0 and r1 (equal variances)
Write down the p-value from this test
(IF time permits : In the lime dataset, test wether treatment with Agricultural Lime has a different effect from treatment with Granular Lime).