E Exercise 03

Last updated: 2026-02-12 16:04:44

E.1 Materials

The materials for this exercise are:

  • Matrices and rasters (Chapter 5)
  • Raster processing (Chapter 6)

E.2 Question 1

  • Calculate the row and the column where the maximum value of the volcano matrix is. Don’t use specific values of row and column indices; instead calculate the required indices in your code.
  • Replace all values in the row to NA
  • Replace all values in the column to NA
  • Replace the value at the row and column with 90
  • Plot the modified volcano using the same method as in Figure 5.2 (Figure E.1)
Modified `volcano` matrix

Figure E.1: Modified volcano matrix

(50 points)

E.3 Question 2

  • Read the raster 'MOD13A3_2000_2019.tif' to a multi-band raster object named r.
  • Calculate a vector of length 24 with the correlation coefficients between the values of the layer 1, and the values of layers 1, 2, …, 24.
  • To calculate correlation coefficients use the cor function with the use='pairwise.complete.obs' argument, as in: cor(x, y, use='pairwise.complete.obs').
  • For example, the 2nd value in the vector should be equal to:
## [1] 0.9752619
  • Plot the values of the vector, as shown in Figure E.2.
  • Note: the two arguments passed to the cor function, i.e., the pixel values of layer 1 and layer n, need to be either vectors or arrays (not matrices). If necessary, a matrix can be converted to a vector with as.vector.
Correlation between NDVI values in layer 1 and layers 1-24

Figure E.2: Correlation between NDVI values in layer 1 and layers 1-24

(50 points)