dessskris Posted September 26, 2011 Report Share Posted September 26, 2011 well as accurate as possible!at least get the shape right... Reply Link to post Share on other sites More sharing options...
Braden Lee Posted September 26, 2011 Report Share Posted September 26, 2011 Ha, the shape is quite right, though I appreciate your concern. When I calculated the accuracy, my program returned 0.99765... The most accurate is a value of 1. I'm just going to go with the discrepancy is of little concern. Thank you. Reply Link to post Share on other sites More sharing options...
agnes Posted October 3, 2011 Report Share Posted October 3, 2011 Hi, Im so lost with this IA I tried different things but i have no idea : ( can someone please please tell me the first equation? then maybe ill figure out the second one.......thanks a tons! Reply Link to post Share on other sites More sharing options...
dessskris Posted October 3, 2011 Report Share Posted October 3, 2011 everyone is likely to get different equations for the first one. anyway we can't give you answers. be more specific with your questions and I'll try to guide you to a certain extent. Reply Link to post Share on other sites More sharing options...
Salve Posted October 5, 2011 Report Share Posted October 5, 2011 Desy, i have a really dumb question. So i got 2 equations from 2 sets of values(3,9) (10,6) which are 6=a*10^b, 9=a*3^b . times ln for both sides i get b=ln6/lna10, and b=ln9/lna3. I then tried set these equations equal each other, ln6/lna10=ln9/lna3, But i dont know how to go from there. Nah it's not a dumb question you better ask than going wrong Ok I cannot work it out for you but I can give you an example with different numbers: After that I suppose you know how to find b Just do it similarly to my method @evanjelly wrong equation.. y=axb How would type this equation to solve for a into the calculator? 1 Reply Link to post Share on other sites More sharing options...
dessskris Posted October 5, 2011 Report Share Posted October 5, 2011 well I'd put this:( (7^(log(2)) /9 )^(1/(log(2) - 1))I hope it works :/ Reply Link to post Share on other sites More sharing options...
grrib Posted October 9, 2011 Report Share Posted October 9, 2011 I found a power function for my first model.. How would I revise it? From what I see, the power function fits the data rather well so I don't really know what to do Reply Link to post Share on other sites More sharing options...
SSJ5Goku Posted October 10, 2011 Report Share Posted October 10, 2011 I found a power function for my first model.. How would I revise it? From what I see, the power function fits the data rather well so I don't really know what to doWhat I'd do is prove that it fits the data well, and then try to revise it anyways, then compare the two functions. Of course, even my math teacher said my portfolio was way-overkill (I literally pulled out all the stops), so I guess it really depends. Either way, imo, if you want to say that it fits the data well, you should prove it fits the data well. And unless you have something like r2 = 0.95ish (which is possible), then you should be able to revise your function... from what I remember. Maybe try making really small tweaks to the function (a +/- 0.01, b +/- 0.01) and seeing how well it fits the data points after that. Then, you just have to give some sort of mathematical rationale for making those changes... Reply Link to post Share on other sites More sharing options...
Shady_Bunny Posted October 11, 2011 Report Share Posted October 11, 2011 I was wondering if anybody has suggestions for alternative software or technology which I could use to model some data. I'm doing a practice G-force portfolio. I heard that excel also works. Does anyone also have any instructions for how I can do this? Thanks a lot! BTW, if anyone has any tips about writing a portfolio could you please tell me as well! ANYTHING would be helpful. I am using a program called geogebra, http://www.geogebra.org/cms, its a free download Reply Link to post Share on other sites More sharing options...
holly Posted October 31, 2011 Report Share Posted October 31, 2011 This is kind of sad... mine was due last week but I'm totally stuck on all this. I need to find the first function that models the graph (the horizontal one). I've been trying to read most of the responses, but it seems like I'm the only one who doesn't get most of the math terminology used... what is the r value that everyone is trying to find? How can I find a function that matches the data given...? I don't understand... am I just supposed to plug in a bunch of random numbers into an equation and hope that it matches? Reply Link to post Share on other sites More sharing options...
dessskris Posted October 31, 2011 Report Share Posted October 31, 2011 This is kind of sad... mine was due last week but I'm totally stuck on all this. I need to find the first function that models the graph (the horizontal one). I've been trying to read most of the responses, but it seems like I'm the only one who doesn't get most of the math terminology used... what is the r value that everyone is trying to find? How can I find a function that matches the data given...? I don't understand... am I just supposed to plug in a bunch of random numbers into an equation and hope that it matches? R^2 value is a number that tells you how accurate your model is. it ranges from 0 to 1, 1 representing the most accurate value. this is not a must, but if your graphing software or excel can show this, you can discuss it. but this is for the technology model. for the first one, you have to generate a model on your own. what model/function? it's up to you to choose. you want to model quadratic? logarithmic? power? or anything you think will fit the data best. then, state the general form of the function and model it. for example, the general form of a linear model would be y=mx+c, the general form of a quadratic model would be y=ax^2+bx+c. now how to generate the function? this is where the difficulty lies. say you want to choose quadratic, you can choose 3 data points from your data, plug in each set of values of x and y, and solve the 3 equations (example of the form of equation you should get: 4a+2b+c=3) using matrices or elimination and substitution. after you get a b c, plug them into the general equation and you're done that's it for how to generate a function analytically. any question just ask. but please quote me so I get a notification and can reply as soon as I log in (I always check my notif but I rarely check new posts in the forum). good luck! 5 Reply Link to post Share on other sites More sharing options...
holly Posted November 1, 2011 Report Share Posted November 1, 2011 any question just ask. but please quote me so I get a notification and can reply as soon as I log in (I always check my notif but I rarely check new posts in the forum). good luck! I'm afraid you might be getting a LOT of notifications, then! Hope you don't mind ! & I will have to work on this tomorrow because of other homework... but I used LoggerPro, plot the points, and just selected a function (I think it's Y=A/x^B+C and there's an option to toggle the values of A, B, and C). So I didn't use algebra or any math... am I allowed to say that I just used "technology"? Or should I also find it by hand as well? Reply Link to post Share on other sites More sharing options...
dessskris Posted November 1, 2011 Report Share Posted November 1, 2011 I'm afraid you might be getting a LOT of notifications, then! Hope you don't mind ! & I will have to work on this tomorrow because of other homework... but I used LoggerPro, plot the points, and just selected a function (I think it's Y=A/x^B+C and there's an option to toggle the values of A, B, and C). So I didn't use algebra or any math... am I allowed to say that I just used "technology"? Or should I also find it by hand as well? that's totally fine they can be deleted anyway so I don't see any problem! well if you noticed the task actually asks for 3 models, two for the data from the first table and one for the data from the other table. from those two functions, one is modelled mathematically, algebraically, whereas the other (the second) one is modelled technologically, with the method you just described. so you still have to do it analytically although you can keep what you've found from there for your second model. Reply Link to post Share on other sites More sharing options...
holly Posted November 8, 2011 Report Share Posted November 8, 2011 that's totally fine they can be deleted anyway so I don't see any problem! well if you noticed the task actually asks for 3 models, two for the data from the first table and one for the data from the other table. from those two functions, one is modelled mathematically, algebraically, whereas the other (the second) one is modelled technologically, with the method you just described. so you still have to do it analytically although you can keep what you've found from there for your second model. Hey! I tried to plug in 3 different data points into the formula I want to use, but then I have to find 3 separate variables (a, b, n). Can I do use matrices for this? b is an exponent in the denominator. Should I just multiply everything about a common multiple to take out the fraction? Or, how would I do this using substitution? Sorry I'm not... too bright. Reply Link to post Share on other sites More sharing options...
dessskris Posted November 8, 2011 Report Share Posted November 8, 2011 Hey! I tried to plug in 3 different data points into the formula I want to use, but then I have to find 3 separate variables (a, b, n). Can I do use matrices for this? b is an exponent in the denominator. Should I just multiply everything about a common multiple to take out the fraction? Or, how would I do this using substitution? Sorry I'm not... too bright. I'm not bright either, I'm somewhat yellow or maybe light brown. it depends on the type of function you're modelling. polynomial functions can be generated through matrices. otherwise I'm afraid the process would be more complicated. generally if you have 3 variables (other than your x and y), you'll need to use 3 data points to find the function. substitute in each set of values of x and y to the general equation/formula, and then solve them simultaneously. you can use elimination or substitution. if you have any other question please just ask ok Reply Link to post Share on other sites More sharing options...
IB 2012 Posted November 23, 2011 Report Share Posted November 23, 2011 Hey! I tried to plug in 3 different data points into the formula I want to use, but then I have to find 3 separate variables (a, b, n). Can I do use matrices for this? b is an exponent in the denominator. Should I just multiply everything about a common multiple to take out the fraction? Or, how would I do this using substitution? Sorry I'm not... too bright. I'm not bright either, I'm somewhat yellow or maybe light brown. it depends on the type of function you're modelling. polynomial functions can be generated through matrices. otherwise I'm afraid the process would be more complicated. generally if you have 3 variables (other than your x and y), you'll need to use 3 data points to find the function. substitute in each set of values of x and y to the general equation/formula, and then solve them simultaneously. you can use elimination or substitution. if you have any other question please just ask ok I graphed the function but I do not know on which trends to comment? Please help!!! Reply Link to post Share on other sites More sharing options...
IB 2012 Posted November 23, 2011 Report Share Posted November 23, 2011 Logistic doesn't work using technology. Are reciprocal functions and power functions the same thing? Another question...when the task says "Use technology to find ANOTHER function that models the data.", can it be another power function with slightly different a and b values that you calculated by hand in the first part? Or does the function have to be a completely different type? Thanks it does work! look at this picture below: it's a logistic regression generated using technology Reciprocal is a form of power function. Reciprocal function is a power function but power function is not a reciprocal function.. Power: y=axb Reciprocal: y=a/x which is y=ax-1 so in a reciprocal function, the b is -1 well it's a bit vague as the task does not clearly mention the type of function looking at the question I think you can model the same type of function. but I personally recommend modelling a different type of function, to demonstrate your broad knowledge in types of function so a completely different one like log or exponential? Reply Link to post Share on other sites More sharing options...
dessskris Posted November 23, 2011 Report Share Posted November 23, 2011 I graphed the function but I do not know on which trends to comment? Please help!!!what do you mean you don't know? do you even see any trend/pattern? if yes, describe what you see. is it increasing/decreasing? any stationary points? visible inflexion? asymptote?so a completely different one like log or exponential?doesn't have to be COMPLETELY different. for example you can do poly 3 at first, then now poly 4. but try to find the best one for your technology model. Reply Link to post Share on other sites More sharing options...
sljj Posted November 24, 2011 Report Share Posted November 24, 2011 (edited) My teacher asked us to find our model fucntion without the use of technology. How do I find it? Is it anything thing to do find find the gradients(slopes), asympotes... ...From the evidence, I'm supposed to create a model function. Edited November 24, 2011 by sljj Reply Link to post Share on other sites More sharing options...
dessskris Posted November 24, 2011 Report Share Posted November 24, 2011 My teacher asked us to find our model fucntion without the use of technology. How do I find it? Is it anything thing to do find find the gradients(slopes), asympotes... ...From the evidence, I'm supposed to create a model function.yes you are asked to model a function without using technology in the first part, meaning you can't use the calculator to find the best regression. but when you need to use matrices, you may solve the matrices using calculator.well you need to determine first what type of function you want to model. then, you can read the explanation already given in this thread or ask. Reply Link to post Share on other sites More sharing options...
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