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These are the user uploaded subtitles that are being translated: 1 00:00:00,690 --> 00:00:06,000 Hello everyone and welcome to lecture on comparison operators in this lecture we're going to learn how 2 00:00:06,000 --> 00:00:10,530 to use comparison operators to compare variables that return logical values. 3 00:00:10,530 --> 00:00:13,950 Let's go ahead and see some examples by jumping to our studio. 4 00:00:13,950 --> 00:00:18,340 All right let's start off by just going through each of the comparison operators. 5 00:00:18,360 --> 00:00:20,340 You're pretty self-explanatory. 6 00:00:20,340 --> 00:00:23,260 So we'll just use simple integers to explain them for us. 7 00:00:23,520 --> 00:00:28,820 Let's say you wanted to get a comparison of five is greater than six. 8 00:00:28,820 --> 00:00:30,970 This should return a logical value. 9 00:00:30,990 --> 00:00:38,290 In this case false to 1 do less then it's just going to be the reverse less sense so 5 less than six 10 00:00:38,290 --> 00:00:39,160 . 11 00:00:39,420 --> 00:00:40,670 True. 12 00:00:40,830 --> 00:00:44,170 Now you can also do greater than or equal to or less than or equal to. 13 00:00:44,370 --> 00:00:52,260 By using something that looks like this or something that looks like this looks for greater than or 14 00:00:52,260 --> 00:00:53,500 equal to. 15 00:00:54,210 --> 00:00:58,890 So you just tack on an equal sign to the less than or greater than sign. 16 00:00:58,890 --> 00:01:02,930 Now you can also do comparisons for equality or inequality. 17 00:01:03,090 --> 00:01:10,740 You can do that with equality for two equal sides so if you want to check let's say if two was equals 18 00:01:10,740 --> 00:01:16,050 equals to three that's going to be a CheckFree quality in this case it's false. 19 00:01:16,050 --> 00:01:20,340 If you just use one equal sign you should get some sort of error because you're basically trying to 20 00:01:20,340 --> 00:01:21,680 do some sort of assignment here. 21 00:01:21,790 --> 00:01:23,180 Is getting it to. 22 00:01:23,250 --> 00:01:26,530 Just remember it's two equal signs for equality. 23 00:01:26,580 --> 00:01:28,870 Do you want to test for any. 24 00:01:29,070 --> 00:01:37,970 You use an exclamation points or exclamation mark with an equal sign so as to not equal to four. 25 00:01:38,070 --> 00:01:42,060 That's true is to not equal to two. 26 00:01:42,120 --> 00:01:43,220 That's false. 27 00:01:43,530 --> 00:01:46,430 And again for equality just two equal signs. 28 00:01:46,530 --> 00:01:47,120 All right. 29 00:01:47,310 --> 00:01:52,960 Something they should pay close attention to is your spacing out when comparing numbers. 30 00:01:53,130 --> 00:02:02,330 Because if you remember correctly the assignments operator for R is this arrow symbol. 31 00:02:02,610 --> 00:02:05,920 So let's say I want to assign 2 to V. 32 00:02:05,940 --> 00:02:07,190 That's how it works. 33 00:02:07,410 --> 00:02:13,470 But let's say I actually have the equal to 2 and I want to compare V. 34 00:02:13,860 --> 00:02:18,300 I want to ask if the is less than negative 1. 35 00:02:18,300 --> 00:02:22,760 Notice here how the spacing is going to play a major role here. 36 00:02:22,770 --> 00:02:27,610 Here I am saying is be less than negative 1 and the answer is false. 37 00:02:27,640 --> 00:02:34,110 If I'm not paying close attention to my spacing and do something like this you're actually going to 38 00:02:34,110 --> 00:02:37,860 do a reassignments of the so that you'll save the. 39 00:02:37,950 --> 00:02:40,580 A sign one value. 40 00:02:40,620 --> 00:02:42,090 So notice the difference here. 41 00:02:42,090 --> 00:02:47,640 This is kind of important otherwise you may mess up your code later on if you have some variable name 42 00:02:47,640 --> 00:02:48,920 . 43 00:02:49,620 --> 00:02:51,410 Just go ahead and put in. 44 00:02:51,570 --> 00:02:57,840 Let's say my VCR and you're trying to do a comparison to a negative number. 45 00:02:57,840 --> 00:03:00,490 Make sure your spacing makes sense for that. 46 00:03:00,690 --> 00:03:06,480 So you always want to make it very clear that you're comparing to a negative number. 47 00:03:06,480 --> 00:03:10,200 Or if you're trying to do some sort of reassignments 48 00:03:14,550 --> 00:03:21,240 so please pay close attention here to the differences of the reassignments versus the comparisons. 49 00:03:21,270 --> 00:03:23,560 OK so that's just a little hiccup. 50 00:03:23,570 --> 00:03:24,840 You may find in the future. 51 00:03:24,870 --> 00:03:29,340 These should probably be paying attention to if you're ever doing some sort of less than comparison 52 00:03:29,340 --> 00:03:32,040 with negative numbers living on. 53 00:03:32,190 --> 00:03:36,030 I want to show you now how you can use comparison operators with vectors. 54 00:03:36,300 --> 00:03:41,940 So when you use a vector with a comparison operator instead of returning just a single logical true 55 00:03:41,940 --> 00:03:42,870 or false value. 56 00:03:43,050 --> 00:03:46,590 It's actually to return an entire vector of logical values. 57 00:03:46,590 --> 00:03:47,640 Let's go ahead and show this. 58 00:03:47,640 --> 00:03:55,170 By creating a vector We'll start by just using the combined function to create a vector of 1 2 3 4 5 59 00:03:55,170 --> 00:03:56,410 . 60 00:03:56,580 --> 00:04:01,780 Now let's say I wanted to compare the less than 2. 61 00:04:01,800 --> 00:04:02,730 What's this going to do. 62 00:04:02,730 --> 00:04:03,260 It's going to do. 63 00:04:03,330 --> 00:04:06,000 Elements by elements comparison. 64 00:04:06,240 --> 00:04:12,030 So it's going to compare all those elements and then return a vector of logical values with the index 65 00:04:12,030 --> 00:04:13,800 referring to the comparison. 66 00:04:13,830 --> 00:04:15,400 So was one less than two. 67 00:04:15,420 --> 00:04:15,970 That's true. 68 00:04:15,990 --> 00:04:16,950 Was 2 less than 2. 69 00:04:16,950 --> 00:04:19,490 That's false false false etc.. 70 00:04:19,620 --> 00:04:22,960 So let's say I wanted to check for equality. 71 00:04:24,570 --> 00:04:29,130 I can do this and it's actually going to return a vector of logical values. 72 00:04:29,340 --> 00:04:34,320 Later on we're going to see how we can Easy's vector comparisons to actually select parts of the vector 73 00:04:34,320 --> 00:04:34,440 . 74 00:04:34,560 --> 00:04:37,190 Which is why we're explaining them now. 75 00:04:37,600 --> 00:04:39,760 OK so that's really all there is. 76 00:04:39,810 --> 00:04:44,830 As far as comparison operators should be pretty straightforward and self-explanatory. 77 00:04:44,970 --> 00:04:48,730 You just have the greater than sign. 78 00:04:49,440 --> 00:04:55,820 You have the less than sign you have greater than or equal to less than or equal to now. 79 00:04:55,860 --> 00:05:01,410 Checks for equality of two equal signs checks for inequality of an exclamation sign with an equal sign 80 00:05:01,420 --> 00:05:01,640 . 81 00:05:01,950 --> 00:05:08,420 And then you can also use the same comparison operators on entire vectors against a single number. 82 00:05:08,790 --> 00:05:14,850 All right last thing I want to mention is that you can actually do element by element comparisons for 83 00:05:15,090 --> 00:05:16,370 multiple vectors. 84 00:05:16,410 --> 00:05:19,720 So let's say I want to compare vector against another vector. 85 00:05:20,190 --> 00:05:21,720 So I have my first vector. 86 00:05:21,770 --> 00:05:27,490 The let's go ahead and assign the two use combined function. 87 00:05:27,510 --> 00:05:37,860 Now let's go ahead and make 10 20 30 40 50 so I can actually compare the one on an element by element 88 00:05:37,860 --> 00:05:41,720 basis to the two. 89 00:05:41,730 --> 00:05:47,070 So I say go ahead and say it is whereas V less than the two. 90 00:05:47,460 --> 00:05:50,220 So you get all five trues which makes sense. 91 00:05:50,220 --> 00:05:56,340 The in every single index location when you compare it on an element bilat basis to be 2 is always less 92 00:05:56,340 --> 00:05:57,150 than the two. 93 00:05:57,270 --> 00:05:58,390 So one is less than 10. 94 00:05:58,400 --> 00:05:59,390 Two is less than 20. 95 00:05:59,430 --> 00:06:00,450 Cetera. 96 00:06:00,450 --> 00:06:03,120 So just like when you compare it to a single value. 97 00:06:03,330 --> 00:06:06,120 A vector by vector comparison operation. 98 00:06:06,240 --> 00:06:12,310 Basically also works the same way in returning a vector full of logical boolean values. 99 00:06:12,630 --> 00:06:15,360 Ok that's it for this lecture. 100 00:06:15,360 --> 00:06:20,670 Again just a quick reminder make sure you pay attention if you're ever doing a comparison that's something 101 00:06:20,670 --> 00:06:27,330 similar to less than a negative number so you're not actually doing a reassignments. 102 00:06:27,570 --> 00:06:29,350 All right thanks everyone. 103 00:06:29,370 --> 00:06:30,180 I'll see you at the next lecture 9823