landsat NDVI time series plot in R, based on point or pixel

Question

I am using R language and I would like to create a NDVI time series plot, NDVI vs time, based on irregular intervaled landsat images. I have found a method to create a raster stack and plot the average NDVI of the total area over time. Average NDVI is okay, but i would like to plot for a selected point (pixel based or xy coordinate) within the area.

Any suggestion? I am very new to R so a step by step explanation would be really helpful

Answer 1

Do you want an interactive map, or are you fine with plotting the NDVI timeseries for one (or few) specific points? In the latter you raster::extract() the NDVI-Stack values under your points, and use the returned dataframe as input for your plot.

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Edit:

I was thinking... You actually can do some interactive point-selection using raster::click(). So as a little example I just wrote this for you:

library(raster)
# Sample Dataset
year2000 <- raster(nrows=10, ncols=10, vals=runif(100, -1,1))
year2005 <- raster(nrows=10, ncols=10, vals=runif(100, -1,1))
year2010 <- raster(nrows=10, ncols=10, vals=runif(100, -1,1))
year2015 <- raster(nrows=10, ncols=10, vals=runif(100, -1,1))

NDVI.stack <- stack(year2000, year2005, year2010, year2015)  # Representing your layerstack

# Plot Stack, select point and automaticly extract values
plot(NDVI.stack[[1]])  # One exemplary layer for orientation
values <- click(NDVI.stack, n=1)

# Compose and plot dataframe
timeseries <- data.frame(year = c(2000, 2005, 2010, 2015),
                         values = values[1, ])
plot(timeseries, type="l")