WEBVTT 00:00:07.690 --> 00:00:09.970 YOSSI FARJOUN: This is Dr. MATLAB, Lecture 1-- 00:00:09.970 --> 00:00:13.540 Using MATLAB for the First Time. 00:00:13.540 --> 00:00:15.340 When you turn MATLAB on for the first time, 00:00:15.340 --> 00:00:18.920 you'll be greeted with a window that looks like this. 00:00:18.920 --> 00:00:20.980 The first thing we do is close all the windows 00:00:20.980 --> 00:00:24.370 that we don't need initially-- 00:00:24.370 --> 00:00:28.420 Current Directory, Workspace, and Command History. 00:00:28.420 --> 00:00:30.740 We're left with a command window. 00:00:30.740 --> 00:00:32.150 This is the command prompt. 00:00:32.150 --> 00:00:38.901 And this is the flashing cursor where our input will be placed. 00:00:38.901 --> 00:00:40.650 The first thing we want to do is try using 00:00:40.650 --> 00:00:42.630 MATLAB as a giant calculator. 00:00:42.630 --> 00:00:46.635 So for example, we can ask MATLAB to calculate 1 plus 1. 00:00:46.635 --> 00:00:48.540 The answer is 2. 00:00:48.540 --> 00:00:51.350 So we type what we want, 3 plus 4. 00:00:51.350 --> 00:00:55.800 Hit Enter and we get the answer-- 00:00:55.800 --> 00:01:04.503 3 times 4, 1 plus 2 times 3, 2 to the power of 4, 00:01:04.503 --> 00:01:09.050 5 to the power of 3, et cetera. 00:01:09.050 --> 00:01:12.920 We can also ask whether two numbers are the same, 00:01:12.920 --> 00:01:15.000 or whether one is greater than the other. 00:01:15.000 --> 00:01:18.760 So to see if 4 is greater than 5, we type this. 00:01:18.760 --> 00:01:20.280 This will tell us that the answer 00:01:20.280 --> 00:01:24.140 is no, 4 is not greater than 5. 00:01:24.140 --> 00:01:26.240 We can ask is 4 less than 5. 00:01:26.240 --> 00:01:28.629 The answer is yes, 4 is less than 5. 00:01:33.320 --> 00:01:36.470 Sometimes we need a function and expression, not just 00:01:36.470 --> 00:01:37.740 an operator. 00:01:37.740 --> 00:01:39.357 So for example, to find the remainder, 00:01:39.357 --> 00:01:40.690 we need to use the function rem. 00:01:40.690 --> 00:01:44.000 Here is the remainder of 15 when divided by 4-- 00:01:44.000 --> 00:01:45.200 rem(15,4). 00:01:45.200 --> 00:01:48.170 The answer is 3. 00:01:48.170 --> 00:01:50.480 To find out more about a function, 00:01:50.480 --> 00:01:52.430 we use the help command. 00:01:52.430 --> 00:01:57.350 help rem will tell us everything we need to know about rem-- 00:01:57.350 --> 00:01:59.080 the remainder after division. 00:01:59.080 --> 00:02:03.080 There's a bit of an explanation, some conventions. 00:02:03.080 --> 00:02:04.220 And the "see also"-- 00:02:04.220 --> 00:02:07.190 this is perhaps one of the most important parts of the help 00:02:07.190 --> 00:02:09.860 file-- is to help you find other commands that 00:02:09.860 --> 00:02:12.560 are useful and related to this command. 00:02:12.560 --> 00:02:15.340 I encourage you to try to find the difference between mod 00:02:15.340 --> 00:02:15.840 and rem. 00:02:18.930 --> 00:02:20.400 Other than calculating expressions, 00:02:20.400 --> 00:02:22.950 we can also assign their value into variables. 00:02:22.950 --> 00:02:26.270 So for example, if I want to create a variable named x, 00:02:26.270 --> 00:02:29.200 I type x equals and then the value that I want. 00:02:29.200 --> 00:02:35.130 So for example, x=1 will create a variable called x and put 1 00:02:35.130 --> 00:02:37.480 as the value into it. 00:02:37.480 --> 00:02:40.410 I can also put the result of an expression into a variable. 00:02:40.410 --> 00:02:41.160 Here's y=2*3. 00:02:43.847 --> 00:02:44.680 Of course, that's 6. 00:02:44.680 --> 00:02:47.825 So it calculates the 6 and puts 2 times 3 into it. 00:02:47.825 --> 00:02:51.080 So now y is 6 and x is 1. 00:02:51.080 --> 00:02:54.675 And I can use x and y if they are numbers. x+y, 00:02:54.675 --> 00:02:56.610 the answer is 7. 00:02:56.610 --> 00:02:58.750 If I try to use a variable that doesn't yet exist, 00:02:58.750 --> 00:03:02.880 for example z+y, I get an error-- 00:03:02.880 --> 00:03:05.660 undefined function or variables. 00:03:05.660 --> 00:03:08.450 Sometimes, you're looking for a command 00:03:08.450 --> 00:03:09.810 but you don't know the command. 00:03:09.810 --> 00:03:11.601 You know that you're looking for something, 00:03:11.601 --> 00:03:13.700 bu you just don't know what it's called in MATLAB. 00:03:13.700 --> 00:03:16.425 In that case, you should be using lookfor 00:03:16.425 --> 00:03:18.050 to find the command you're looking for. 00:03:18.050 --> 00:03:22.790 So for example, lookfor square will give you 00:03:22.790 --> 00:03:27.350 all the commands that have the word square in their help file. 00:03:27.350 --> 00:03:31.346 Of course, I was looking for, in this case, square root. 00:03:31.346 --> 00:03:31.970 And here it is. 00:03:31.970 --> 00:03:33.800 I can either click on this and that 00:03:33.800 --> 00:03:37.580 will give me the help file of the square root. 00:03:37.580 --> 00:03:41.630 Or I can just type help sqrt. 00:03:41.630 --> 00:03:44.850 And that will give the same. 00:03:44.850 --> 00:03:47.950 Square root finds the square of the elements. 00:03:47.950 --> 00:03:51.960 So if I do sqrt(4), I get 2. 00:03:51.960 --> 00:03:54.120 Notice that I get complex results 00:03:54.120 --> 00:03:57.030 if I get a non-positive input. 00:03:57.030 --> 00:04:05.400 So sqrt(-3) is the square root of three times i, which is, 00:04:05.400 --> 00:04:06.720 of course, very nice to know. 00:04:06.720 --> 00:04:15.240 So 2i^2 should give me -4, and indeed, 2i squared gives me -4. 00:04:15.240 --> 00:04:17.399 On the command line, there is a useful trick 00:04:17.399 --> 00:04:19.300 involving the "up" button. 00:04:19.300 --> 00:04:21.690 Sometimes, you're looking for something 00:04:21.690 --> 00:04:27.740 or you're typing something and you make a typo, like this. 00:04:27.740 --> 00:04:29.250 I've swapped the L and the E. Now 00:04:29.250 --> 00:04:30.900 I could retype everything from scratch, 00:04:30.900 --> 00:04:33.030 or I can press the up key-- 00:04:33.030 --> 00:04:40.820 up arrow-- and then the left arrow until I can delete the E, 00:04:40.820 --> 00:04:42.440 and put it in the right place. 00:04:42.440 --> 00:04:47.720 Now when I hit Enter and I get the help info. 00:04:47.720 --> 00:04:49.280 With the up arrow and the down arrow, 00:04:49.280 --> 00:04:53.300 I can browse through the history of all the commands that I did. 00:04:57.340 --> 00:05:00.200 If I have a longish expression on the command line 00:05:00.200 --> 00:05:01.910 and I want to erase the whole thing, 00:05:01.910 --> 00:05:04.040 I could start erasing it. 00:05:04.040 --> 00:05:11.360 Or I could press Control-C. 00:05:11.360 --> 00:05:13.040 That's probably enough for today. 00:05:13.040 --> 00:05:18.030 To exit MATLAB, I either look for the Quit MATLAB here 00:05:18.030 --> 00:05:23.580 or I can Apple-Q. Or from the command line, I can type exit.