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These are the user uploaded subtitles that are being translated: 1 00:00:00,570 --> 00:00:05,490 Hello everyone and welcome to the Creating a matrix lecture before you learn about the various data 2 00:00:05,490 --> 00:00:06,380 types in our. 3 00:00:06,420 --> 00:00:12,300 And we've also learned about vectors which allow us to store indexed elements matrix is going to allow 4 00:00:12,300 --> 00:00:17,740 us to have to them actual data structures which contain elements consisting of the same data type. 5 00:00:17,760 --> 00:00:22,500 Let's go ahead and jump to our studio to explore how to create a matrix. 6 00:00:22,500 --> 00:00:22,990 OK. 7 00:00:23,040 --> 00:00:24,740 So here are our studio. 8 00:00:24,750 --> 00:00:30,240 And before we actually talk about The Matrix I want to show you a quick tip for quickly creating sequential 9 00:00:30,240 --> 00:00:36,120 numeric vectors you can use the colon notation similar to the slicing notation to actually create a 10 00:00:36,120 --> 00:00:38,540 sequential vector of numerics. 11 00:00:38,550 --> 00:00:47,490 So for example if I go ahead and type into the console one Clinton I get out a vector that sequential 12 00:00:47,580 --> 00:00:51,590 integers that goes from 1 to 10. 13 00:00:51,690 --> 00:00:53,010 So this is a nice trick. 14 00:00:53,160 --> 00:00:57,640 They'll help you save a lot of time when you're creating these sequential numeric vectors. 15 00:00:57,780 --> 00:01:01,380 And then you can assign this to a variable. 16 00:01:01,380 --> 00:01:09,640 So for instance if I do this sort of assignments I've actually created quickly a vector of numeric sequence 17 00:01:09,650 --> 00:01:10,090 . 18 00:01:10,110 --> 00:01:10,530 All right. 19 00:01:10,860 --> 00:01:15,400 So now that we know that little trick that's going to help us a lot with the matrix function. 20 00:01:15,480 --> 00:01:21,430 So to create a matrix and are used the matrix function and the capacitate vector to it. 21 00:01:22,050 --> 00:01:27,090 So I'm going to go in and say matrix and then I'm going to go ahead and pass in the data in this case 22 00:01:27,180 --> 00:01:32,650 the first thing to do is just pass in the vector and we'll slowly discover the other arguments or parameters 23 00:01:32,660 --> 00:01:32,680 . 24 00:01:32,700 --> 00:01:35,710 We can define in the matrix function. 25 00:01:35,810 --> 00:01:40,230 So now you'll notice that I've created a matrix and notice how it's been printed out. 26 00:01:40,320 --> 00:01:42,260 Now it shows that it's in two dimensions. 27 00:01:42,270 --> 00:01:48,520 We have 10 rows with one column instead of just having this one dimensional array. 28 00:01:48,690 --> 00:01:53,520 So the outputs been displayed as a two dimensional matrix which is 10 rows by one column. 29 00:01:53,820 --> 00:01:56,930 But what if we actually want to specify the number of rows. 30 00:01:57,060 --> 00:02:02,850 So we actually want to specify how we construct this two dimensional matrix from that one the array 31 00:02:02,940 --> 00:02:03,750 vector. 32 00:02:03,920 --> 00:02:10,140 But we can pass a parameter arguments into the matrix called and row which stands for the number of 33 00:02:10,140 --> 00:02:10,940 rows. 34 00:02:10,950 --> 00:02:13,880 So let's go ahead and try this again. 35 00:02:13,950 --> 00:02:22,860 I'm going to clear the console check that is still that vector 1 through 10 call the Matrix on V and 36 00:02:22,860 --> 00:02:26,530 I'm going to go ahead and pass in a parameter and row. 37 00:02:26,850 --> 00:02:29,530 And this just stands for the desired number of rows. 38 00:02:29,760 --> 00:02:35,340 So I'm going to go ahead and say I want two rows to be made from this vector. 39 00:02:35,430 --> 00:02:40,920 And so now a matrix has two rows and says we need to have the correct number of columns in order to 40 00:02:40,920 --> 00:02:42,140 equal 10 elements. 41 00:02:42,180 --> 00:02:46,900 It's going to be five columns since five times two is equal to 10. 42 00:02:46,920 --> 00:02:51,010 So now we've been able to specify a two by five matrix. 43 00:02:51,450 --> 00:02:54,960 Notice how the NRA argument allowed that to happen. 44 00:02:55,110 --> 00:03:00,090 But the other question you may have is how do we actually the side that still order we could have filled 45 00:03:00,090 --> 00:03:02,420 the columns first as we did in this case. 46 00:03:02,430 --> 00:03:04,440 One two three four five six. 47 00:03:04,590 --> 00:03:08,170 But we also could have filled the rows in sequential order. 48 00:03:08,190 --> 00:03:13,120 So for example we could have had that first row been one to three four. 49 00:03:13,140 --> 00:03:14,700 The horizontal. 50 00:03:14,700 --> 00:03:18,480 Do you actually want to specify how you filled the matrix. 51 00:03:18,480 --> 00:03:24,600 Default is by columns B you can say and add a by RHO argument which allows you to see whether or not 52 00:03:24,600 --> 00:03:27,170 you want to fill out the Matrix right rows or columns. 53 00:03:27,180 --> 00:03:30,710 So we're going to show you an example of that. 54 00:03:30,760 --> 00:03:39,600 Going to go ahead and say Matrix and instead of passing and V and then the in a vector that goes from 55 00:03:39,600 --> 00:03:50,490 1 to 12 sequentially using that colon notation and then to go ahead and specify by RHO to be equal to 56 00:03:50,940 --> 00:03:53,430 false which is the default case. 57 00:03:53,850 --> 00:03:57,740 And I'm going to specify a number of rows equal to 4. 58 00:03:58,050 --> 00:04:03,390 So I have four rows meaning I should have three columns and four times three is 12. 59 00:04:03,690 --> 00:04:10,820 And since I said biros equal to false which is the default anyways the matrix is filled by column for 60 00:04:10,810 --> 00:04:10,870 . 61 00:04:10,870 --> 00:04:16,120 So notice how that first column that one column here has 1 2 3 4. 62 00:04:16,320 --> 00:04:19,240 And the second column is 5 6 7 8. 63 00:04:19,290 --> 00:04:22,980 Also pay attention to how this index notation actually looks. 64 00:04:22,980 --> 00:04:28,400 With the comma placements versus the rows and columns here. 65 00:04:28,410 --> 00:04:34,440 So in the rows you get the row number first and then the comma and in the columns you get a comma first 66 00:04:34,560 --> 00:04:36,430 and then the column number. 67 00:04:36,720 --> 00:04:44,350 Later on we'll discuss why that's important for index purposes but for now which lushest us the by row 68 00:04:44,370 --> 00:04:48,470 and the end row let's go ahead and try this same operation. 69 00:04:48,630 --> 00:04:52,160 You'll go ahead and say biros is equal to true. 70 00:04:52,320 --> 00:05:00,900 So don't go ahead and press up on my keyboard and change this false to be a capital T for true. 71 00:05:01,190 --> 00:05:01,750 All right. 72 00:05:02,060 --> 00:05:06,050 So now I said biros equal to T for true. 73 00:05:06,140 --> 00:05:11,180 And I've been able to fill out this matrix by the row first so one two three four five six seven eight 74 00:05:11,180 --> 00:05:12,500 nine etc.. 75 00:05:13,120 --> 00:05:18,410 Now that we've gone over some of the basics of using the matrix function and the additional parameters 76 00:05:18,410 --> 00:05:23,740 inside of it let's go over how we can create matrices from many vectors and then how we can actually 77 00:05:23,750 --> 00:05:25,530 name matrices. 78 00:05:25,550 --> 00:05:30,230 So in order to do this I'm actually going to start writing in our scripts so to bring down the cancelbot 79 00:05:30,920 --> 00:05:34,710 and type into this demo the script that I have here. 80 00:05:34,750 --> 00:05:41,650 Let's go ahead and create two vectors one called g g which will go ahead and pretend that we're working 81 00:05:41,660 --> 00:05:43,920 with stock prices for Google. 82 00:05:43,940 --> 00:05:46,640 These aren't real prices I'm just making them up. 83 00:05:47,340 --> 00:05:52,450 Well let's say we have just a steady rise maybe a little bit of a fall. 84 00:05:52,510 --> 00:05:58,180 So just five stock prices for the five work days going to go ahead and make that into a vector. 85 00:05:58,340 --> 00:06:05,120 Now let's make one more for let's say Microsoft and let's just go ahead and make up some stock prices 86 00:06:05,120 --> 00:06:08,730 . 87 00:06:08,740 --> 00:06:09,340 All right. 88 00:06:09,710 --> 00:06:20,030 So we have two vectors and we can actually combine these into an object called or a variable called 89 00:06:20,020 --> 00:06:20,740 stocks 90 00:06:25,190 --> 00:06:29,100 and we'll use the combined function in this manner. 91 00:06:29,120 --> 00:06:33,980 So now I have my two vectors Google and Microsoft and I'm using the combined function by passing them 92 00:06:33,980 --> 00:06:37,270 in Google Microsoft and then I'm calling that variable stocks. 93 00:06:37,390 --> 00:06:44,150 If I go ahead and say on line 6 to the space stocks and then I'm going to go ahead and run this file 94 00:06:44,140 --> 00:06:45,860 here. 95 00:06:45,860 --> 00:06:49,120 Notice that now in our environment we have this stock's value. 96 00:06:49,190 --> 00:06:55,640 And if I want to see it in the console and I can actually just say print stocks so it's going to run 97 00:06:55,630 --> 00:06:57,420 that so we can see it in the con.. 98 00:06:57,710 --> 00:07:01,120 And notice I have 450 4:31 the Google prices. 99 00:07:01,340 --> 00:07:04,370 And then I got it combined with the Microsoft prices. 100 00:07:04,460 --> 00:07:08,960 So if I actually want to build a matrix out of this I can use the following notation. 101 00:07:08,960 --> 00:07:13,520 I can say stock Matrix 102 00:07:16,060 --> 00:07:24,610 is the matrix function and I can pass in stocks than say by RHO is equal to. 103 00:07:24,640 --> 00:07:26,790 Let's go ahead and just say T for true. 104 00:07:27,620 --> 00:07:32,470 And then I'm going to specify and RHO to be equal to the number two. 105 00:07:32,530 --> 00:07:38,540 So I'm going to say and a row is equal to two. 106 00:07:39,080 --> 00:07:46,090 And let's go ahead and then just printout that stock matrix to see what it looks like. 107 00:07:46,100 --> 00:07:49,240 So it's from that source. 108 00:07:49,250 --> 00:07:54,940 And now we can see here we have this nice little matrix where the first row represents those Google 109 00:07:54,950 --> 00:07:55,950 stock prices. 110 00:07:56,000 --> 00:08:00,470 And the second row represents those Microsoft stock prices. 111 00:08:00,470 --> 00:08:05,570 And now we want to do since we have our nice matrix it actually be nice to name the rows and the columns 112 00:08:05,560 --> 00:08:11,480 for reference and we can actually do this just like we did it for vectors using the names function but 113 00:08:11,480 --> 00:08:17,560 instead of using names we're going to do is use call names and row names in order to specify whether 114 00:08:17,840 --> 00:08:20,040 naming the columns or the rows. 115 00:08:20,060 --> 00:08:24,190 So let's go ahead and work on that part. 116 00:08:24,250 --> 00:08:25,600 So we have that stock matrix. 117 00:08:25,610 --> 00:08:26,730 Let's go ahead and name it. 118 00:08:26,930 --> 00:08:32,030 It's going to be really similar to the way we named the vectors except we have two functions call names 119 00:08:32,020 --> 00:08:32,810 and row names. 120 00:08:32,840 --> 00:08:38,210 Now we have two that mentions Let's go ahead and make a vector called days. 121 00:08:38,210 --> 00:08:48,640 And we're just going to have it be the days of the week so say Monday Tuesday Wednesday Thursday and 122 00:08:48,640 --> 00:08:49,170 Friday 123 00:08:53,210 --> 00:08:59,160 and then we'll also have let's say stock names. 124 00:08:59,990 --> 00:09:07,170 And those are going to be equal to just their tickers which is Google and then MSFC Microsoft. 125 00:09:07,460 --> 00:09:13,670 So have these two vectors which are the names you want and then we're going to go ahead and do is use 126 00:09:13,730 --> 00:09:18,340 the name functions so call names in our stock matrix 127 00:09:21,190 --> 00:09:33,250 and then assign it with days and then similarly foreign names pasand stock matrix and assign it those 128 00:09:33,280 --> 00:09:34,810 ST names. 129 00:09:34,820 --> 00:09:35,780 All right. 130 00:09:35,780 --> 00:09:41,240 And then once you've done that let's go ahead and just print out the stock matrix and see what it looks 131 00:09:41,240 --> 00:09:42,190 like. 132 00:09:42,230 --> 00:09:44,160 So it's going to run that source. 133 00:09:44,870 --> 00:09:50,690 And notice now we have a really nice looking matrix here in the console we have the columns clearly 134 00:09:50,680 --> 00:09:56,180 defined by the days of the week and then the rows clearly names for their stock ticker. 135 00:09:56,200 --> 00:09:57,520 They refer to. 136 00:09:57,620 --> 00:09:58,170 All right. 137 00:09:58,510 --> 00:10:02,770 So it looks like we're really starting to build up a powerful tool that we can use later on. 138 00:10:02,990 --> 00:10:07,790 And you should begin to be reminded of a spreadsheet later on we're going to learn about data frames 139 00:10:07,880 --> 00:10:10,830 another data structure is going to build on top of this idea. 140 00:10:11,000 --> 00:10:15,470 For now that's the basics of actually creating a matrix in the next structure we're going to be building 141 00:10:15,470 --> 00:10:17,380 off this matrix of stock prices. 142 00:10:17,410 --> 00:10:20,340 So go ahead and keep this code for future reference. 143 00:10:20,360 --> 00:10:20,980 Okay. 144 00:10:21,130 --> 00:10:23,020 Thanks everyone and I'll see you at the next lecture 14904