In the video lecture, we talked about a hospital with 400 heart attack patients, of whom 72 died within 30 days, and 328 are still alive. Let's plot the likelihood function for this example. We could use either a binomial likelihood, or a Bernoulli likelihood. These are actually the same, other than a constant term in the front, a combinatoric term for the binomial does not depend on theta. So we'll be getting the same answers, it's just a little rescaling on the vertical axis. It's much simpler to stick with the Bernoulli likelihood that doesn't have the combinatoric terms. The likelihood is a function of the mortality rate theta. So we'll create a function in r, we can use the function command, and store our function in an object. You can call this object likelihood. Use the function command and we specify what arguments this function will have. We'll need total sample size, n, the number of deaths, y, and the value of the parameter theta. We specified the function inside of curly braces. In this case, all we needed to do is return a computed value. So we'll use the return function to return that value and here we just put in the likelihood formula, which in this case, is theta to the y times one minus theta to the n minus y. To plot likelihood will create a sequence of points with mortality rates between zero and one and then plot the likelihood values over that sequence. So I'll define sequence of values for theta is in sequence command. Here we go from 0.01, 2.99, in increments of 0.01. We can now plot this. We're going to call the likelihood function over this sequence, it's an n equals 400, y equals 72 and our vector theta. This pops up a plot. And if we look carefully, we can say that the likelihood is maximized at the value 72 over 400 or 0.18. This might be a little bit difficult to see in the plot. And so, one thing that can help is we can add a vertical line is on the a b line command and say vertical line f point one eight. Adding that in makes it very clearly that this likelihood is maximized at 72 over 400. We can also do the same with the log likelihood. Which in many cases is easier and more stable numerically to compute. We can define a function for the log likelihood, say log like. Which again is a function of n, y and theta. Here, we'll return the value from the log likelihood which is y times the log of theta Plus n minus y times the log of one minus theta. Now we can plot the sequence against the log likelihood of that sequence. [SOUND] It's a smoother function. A little bit more difficult to see where the maximum is. Again, adding the vertical line helps us see the maximum at 0.18. Plotting this as a series of points doesn't give us necessarily the best picture. We could actually do this as a line plot instead. In r, we can use the up arrow to go back to a previous command we've run. So if I hit up three times I can get back to the function or to one of the plots. Here, I can add another argument. The plot command has many, many possible optional arguments. One of them is the type of plot. If I say type equals double quotation lowercase l, that tell us, tells r to make a line plot.