Sabs44 Posted September 29, 2011 Report Share Posted September 29, 2011 I am using a cubic function too. I already substituted each of the coordinates in the cubic model (ax + bx + cx + d....etc etc (imagine it with the exponents)) haha you get the idea. And i was thinking of using a matrix to obtain abcd...the problem is..I don´t really know how to use a matrix to do that. Any help? Just set up a 4x4 matrix with all of the coefficients for a, b, c, and d, and multiply it by a 4x1 matrix of a b c d to get a 4x1 matrix of your y values... then can you solve from there? Reply Link to post Share on other sites More sharing options...
dessskris Posted September 29, 2011 Report Share Posted September 29, 2011 wrong model btw, it's supposed to be: y=ax^3+bx^2+cx+d remember when you need to generate a linear function, knowing two points? for example, you have (1,2) and (3,4). your functions will be: 2=m+c 4=3m+c then, construct matrices. then... you can use inverse to solve for m and c. Reply Link to post Share on other sites More sharing options...
Bradley Posted September 29, 2011 Report Share Posted September 29, 2011 Just a quick question, do they tolerate humor in the IA's at any point?Remembering that an "excellent" IA is aimed at the students peers. Reply Link to post Share on other sites More sharing options...
dessskris Posted September 29, 2011 Report Share Posted September 29, 2011 no... no humour in any kind of IA. don't try to joke around on IB papers!anyway you never know what kind of person will moderate your IA. if they are some strict person, you'll get 0 for criterion F and probably get lower marks at some other criteria. Reply Link to post Share on other sites More sharing options...
Bradley Posted September 29, 2011 Report Share Posted September 29, 2011 So, no mentioning Zombies or the PRC's ideology as the reason the population randomly goes negative... Oh, and Desy, that function I was trying to do kind of defeated me... 1 Reply Link to post Share on other sites More sharing options...
dessskris Posted September 29, 2011 Report Share Posted September 29, 2011 lol no zombies! if it goes below the x-axis, you could probably say this is not a good function, or something like that.oh what's wrong? Reply Link to post Share on other sites More sharing options...
Bradley Posted September 29, 2011 Report Share Posted September 29, 2011 (edited) My school said no extra credit for using something we haven't learnt yet, and I would more likely lose marks for doing it wrong, so I should stick to something simple.And I was going to use dry humor. "Some of the limitations of this model are; that it relies on there being a large number of undead in China between x1 and x2, and on the PRC belief that before the PRC, there were no humans in China. As this sort of happening is preposterous, we can conclude that a model which would have to resort to such stipulations to be highly inaccurate etc." Edited September 29, 2011 by Brad Johnston 1 Reply Link to post Share on other sites More sharing options...
Bradley Posted September 30, 2011 Report Share Posted September 30, 2011 When formatting this IA: can we have paragraphs being widows and orphans (split over two pages)?Should all talk related to a graph/table be on the same page as it?General other formatting questions, is there a guide handy for formatting? Reply Link to post Share on other sites More sharing options...
dessskris Posted September 30, 2011 Report Share Posted September 30, 2011 yes you can. it would be great if they could be on the same page. but anyway you have to label them so if you want to refer to an object not on the same page, you can, by using the label (e.g., Figure 1) and yeah you can refer to this --> Reply Link to post Share on other sites More sharing options...
Sabs44 Posted October 1, 2011 Report Share Posted October 1, 2011 Should the "modified" logistic function for the IMF data be found by using transformations and changes of K, L, and M, or should it simply be found using technology? Reply Link to post Share on other sites More sharing options...
dessskris Posted October 1, 2011 Report Share Posted October 1, 2011 I have to say I'm not very sure, but I think for the IMF data part you need to choose between your analytical model and your technological model, then modify it to fit the IMF data by translation and stretching. once again I'm not 100%, though. Reply Link to post Share on other sites More sharing options...
Sabs44 Posted October 1, 2011 Report Share Posted October 1, 2011 yeah i've decided on my technological model, but i'm just wondering whether I improve it technologically or analytically, by changing the values of K, L, and M manually? Reply Link to post Share on other sites More sharing options...
dessskris Posted October 2, 2011 Report Share Posted October 2, 2011 then modify it to fit the IMF data by translation and stretchingwasn't that clear enough?well since the instruction on the task paper is not specific enough, I guess you could do anything you want. but if you use translation and stretching, it allows you to demonstrate more of your mathematical knowledge and it shows that you are familiar with various methods. Reply Link to post Share on other sites More sharing options...
shyla Posted October 8, 2011 Report Share Posted October 8, 2011 hello, how do you get the parameters of K, L , M. I looked at the pdf posted on the first page but I am still confused o how to get the Parameters.. can someone please help me? p.s What is regression?? Hey. If you have a GDC like TI-83 or TI-84 this should be easy. Go to STATS then then click on edit and enter all the data that was given. The years are too large and makes it harder to graph so you can input 0,5,10,15,20,25,30,35,40,45. These are the exact intervals as the years so the accuracy is fine. After you enter both the year and population value quit and then go back to STATS. Go across to CALC then scroll down all the way to logistic...which is B I believe then press enter then put L1 and L2. Then waalaa you have your parameters. When I followed these instructions, it worked for me, however I even tried plotting it putting the values 1950-1955 instead of 0-45, and I get a different, must steepher graph. In my calculator, only the value for a changes. How come the two graphs are different? If the intervals are the same, shouldn't the graph go through the points? What explains the shape of this graph? Reply Link to post Share on other sites More sharing options...
Olga Gonzalez Posted October 8, 2011 Report Share Posted October 8, 2011 I am using a cubic equation. I already arranged the result of substituting the coordinates in the cubic model and I have organized them in a Matrix. I used the Reduced Row-Echelon form to figure out the inverse Matrix, but the values that come up, when arranged in a cubic function, don´t give out any graph. What am I doing wrong? Reply Link to post Share on other sites More sharing options...
Olga Gonzalez Posted October 8, 2011 Report Share Posted October 8, 2011 wrong model btw, it's supposed to be: y=ax^3+bx^2+cx+d remember when you need to generate a linear function, knowing two points? for example, you have (1,2) and (3,4). your functions will be: 2=m+c 4=3m+c then, construct matrices. then... you can use inverse to solve for m and c. This is my matrix after plugging in coordinates in the cubic model: 0 0 0 1 554.8 8000 400 20 554.8 830.7 42875 1225 35 554.8 1070.0 91125 2025 45 554.8 1220.5 But when I apply the Reducer Row-Echelon form, the results are no good to draw a graph. What am I doing wrong? Reply Link to post Share on other sites More sharing options...
Olga Gonzalez Posted October 8, 2011 Report Share Posted October 8, 2011 I am using a cubic function too. I already substituted each of the coordinates in the cubic model (ax + bx + cx + d....etc etc (imagine it with the exponents)) haha you get the idea. And i was thinking of using a matrix to obtain abcd...the problem is..I don´t really know how to use a matrix to do that. Any help? Just set up a 4x4 matrix with all of the coefficients for a, b, c, and d, and multiply it by a 4x1 matrix of a b c d to get a 4x1 matrix of your y values... then can you solve from there? No...I honestly don't get it. Sorry.... Reply Link to post Share on other sites More sharing options...
Olga Gonzalez Posted October 8, 2011 Report Share Posted October 8, 2011 Do I inverse the 4x4 and 4x1 matrix separately, or do I inverse them in a same matrix? Reply Link to post Share on other sites More sharing options...
Olga Gonzalez Posted October 9, 2011 Report Share Posted October 9, 2011 I don´t understand how to use technology to find K, L and M. I understand what each of them mean, so when I know the numbers I would know how to interpret them, but how do I find them? Any help? Reply Link to post Share on other sites More sharing options...
dessskris Posted October 9, 2011 Report Share Posted October 9, 2011 @shyla I don't quite understand your question. try to use (x-1950) instead of x in your function?@Olga sorry for taking so long to reply. I've been busy these days. use a different point for the first row in your matrix. and why do you always have 554.8 in your other rows? you do 3x4 matrix rref (alternatively you can use inverse) (3x4 means 3 rows, 4 columns). for KLM, just tabulate all your data in your GDC spreadsheet, then use the menu to find best logistic regression... I'm not sure what to press since we might be using different calculators, but if you use TI-Nspire let me know I can give you the instructions. it will then show the general equation form, which is the researcher's model and all the values of the parameters.next time just quote me if you want a reply since I can't always check the forum due to exams coming up. so I will get a notification and can read your question. Reply Link to post Share on other sites More sharing options...
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