For each step, make sure your markdown document prints the relevant output, so that I can see that your code works.

Problem 1

  1. Load the Howell’s craniometric dataset into R. This dataset includes 82 measurements on 2524 human crania from 28 populations (measurement abbreviations detailed in this pdf). Note that a 0 indicates missing data in this dataset, so make sure to specify this when you read in the data.
  2. Evaluate the structure of the dataframe using the str() function to make sure that it got read in correctly. It should have 2524 observations of 86 variables.
  3. Create a new dataframe containing only the XFB, OBB, and SIS varibles
  4. Add a new column to the new dataframe that is the product of the XFB, OBB, and SIS variables.

Problem 2

  1. Using dplyr, calculate the mean of the GOL, XCB, ZYB and SIS measurements for each population group by sex. (i.e., calculate the mean value separately for NORSE males and NORSE females, and likewise for all groups). The resulting data frame should only have 6 columns. (one each for sex and population, and one for each of the 4 measurements).
  2. Recreate the below figure exactly (including the theme) using the full cranial dataset. Note: you can control the size of the figures in your knitted document by including options in the code chunk. The default size is 6 for width and height. The figure below is 16 wide and 9 high, like the following.

    ```{r fig.width=16, fig.height=9}

    #code to make the figure here

    ```