Solve Ordinary Differential Equations in Matlab

[ReturnOfTheMack7]

the units aren't right... it's one thing to say it won't model reality and another to write an equation that doesn't make sense mathematically either.

[jakeblanchard]

@ReturnOfTheMack7

The units are fine. Of course, some of the numbers (like 4/15) are not dimensionless.

[ReturnOfTheMack7]

@jakeblanchard a number does not have units... no one should assume you have 'hidden' the correct units behind the fraction. you should leave it as a variable and explain the number and units [kg/m] as you do with m and g.

[uoweme5grand]

let`s say the function has consists of time being squared. so the dy/dt function has a t in it. would ode 45 still work?

[tomtomtramp]

Thanks for the vids! But I'm writing the wrong code. I am developing a system to analysis the rocking motion of a block subjected to an earthquake excitation. The state vector is y(t)={theta(t) , theta'(t)}. and the Time-derivative vector f(t) is y'(t)= {theta'(t) , p^2(sin(alpha*sgn[theta(t)]-th­eta(t))+u''/g*cos(alpha*sgn[th­eta(t)]-theta(t))]}. I have the values for p, alpha, u'' and g. But I need theta(t), and theta'(t). theta(t) is the rotation angle to time, t. Please help, I need it!

[jillukevin]

sir even if iam using the exact equation and coding as shown in this video it says input argument ' y ' is undefined . im new to this can u help me sir

[jakeblanchard]

@jillukevin

I would suggest you go to the link below and download the scripts. They should work for you. Sorry for the strange typing, but I've never figured out how to get a good link into a YouTube comment. I guess they are afraid of Spam, so they forbid the posting of links.

blanchard "dot" ep "dot" wisc "dot" edu/PublicMatlab/index.html#IV­P

[lifeson32]

Clear and thorough. Thanks so much!

[patrickimo1]

Excellent introduction, very straightforward. Thanks for posting this!

[baderb52]

Life saver indeed

[warfood]

Your videos are easy to follow and cover topics thoroughly. You sir, are an amazing teacher.

[nbsr1]

50m/s, poor paratrooper.

[ukoba]

is it possible for me to download this movie? how should I go about this

[jakeblanchard]

@ukoba

I don't know of any way to do this directly. When I want to "download" a flash video, I use a screen capture utility. Lately I've been using TipCam, but there are others, including some web-based tools. Let me know if you need details.

[wjpinto]

@jakeblanchard

If you use Firefox, you need to install the following complement: DownloadHelper (there are other options) and when you're watching the video, appears on the screen, an icon at the bottom of the addon where you can download the video at the size you want.

Or you can use aTubeCatcher too.

[wjpinto]

jakeblanchard

If you use Firefox, you need to install the following complement: DownloadHelper (there are other options) and when you're watching the video, appears on the screen, an icon at the bottom of the addon where you can download the video at the size you want.

Or you can use aTubeCatcher too.

[RainbowFuckingRndlph]

@ukoba You can install "orbit downloader" or "free youtube downloader"

links are:

orbitdownloader (dot) com

youtubedownloader (dot) com

The only thing you have to do after installing the program is to copy & paste a flash movie link.

[FallofDarkness55]

@ukoba are you talking about downloading this youtube video? if so then just go to either clipnabber (dot) com or savevid (dot) com. remember to replace the (dot) with the actual period on your keyboard and no spaces. copy the video url in your browser and paste it in the savevid or clipnabber box and click nab in clipnabber or save video. hope this helps you.

[orion1077]

@ukoba

there is a pprgam called "youtube downloader"...google it

alternativelly you can install real player...even the free version allows you to download things from outube (the will be an option in the begining of the instalation)

[guitarcoweb]

Why would I be getting this after I finish the problem:

??? Undefined function or variable 't'.

Error in ==> f at 1

rk=f(t,y);

I was wondering why you would use "rk" for the function..

I'm a completely brand new user, and the professor I'm working for wants me to master solving differential equations of matlab, and right now it's way over my head.

[jakeblanchard]

@guitarcoweb

I'm not sure where that error is coming from. I would have to see all your code. Feel free to send it to me and I can try to take a look.

The rk stands for Runge-Kutta. This is the name of the algorithm that ode45 uses to solve the equations. You can use just about anything you want.

[FriskyBat]

Spiffing tutorial, old bean!

[nitinbadare]

its a good v deo

[zelda54545]

you have made a mistake in the script, on the solution slide, on line four the @f should be written as '@f '... , by to clarify you have produce two m-files; one saved as a function data and the second one as the solution script is that correct way to go? let me know cheers

[jakeblanchard]

@zelda54545

No, it is correct as it is written. If you are using a file called f.m, the old way to refer to it was 'f' but now they are moving towards @f. But when you use @f, you don't use any single quotes.

You can put f.m in a separate file, or you can put it in the same file. To do the latter, look in the next comment.

[jakeblanchard]

@jakeblanchard

Once again, youtube won't post my script and won't tell me why. This is very annoying. If you want a working script with everything in one file, download the file called

ode2ndOrder.m

from

blanchard "dot" ep "dot" wisc "dot" edu/PublicMatlab/#IVP

[mausamverma]

Dr. Blanchard,

Your tutorials are very clear and ideal for beginners but at the same time crucial for advanced users. Please keep posting more of these as this is very noble way of spreading knowledge in addition to your university stage.

God bless you.

Thanks a lot

[ALDabbagh1988]

Thank you VERY MUCH sir for your help, it totaly helped me. God bless you

[MIssssLate]

I am very sorry, when I do this I get this error, ??? Undefined function or variable 'V'.

Error in ==> d at 4

rk=-g+((4/15)*(V^2)/mass);

what shall I do, and what is the problem, if anyone could help.... pleaseeeee... ))))

[jakeblanchard]

@MIssssLate

That is a "y" not a "V"

[MIssssLate]

aaaa... ok... thank you very much!!! I get this now.. I am stupid.. sorry!!!

[jakeblanchard]

@MIssssLate

By the way, you can download a working script at

blanchard "dot" ep "dot" wisc "dot" edu "slash" PublicMatlab

(Sorry about the formatting. Youtube has a very annoying policy against URLs in comments.)

[MIssssLate]

Thank you very much!!!

[MIssssLate]

Sorry, can anyone plz tell, me do I have to put END in the end??? Thank u!!!!!!!!!!!

[jakeblanchard]

@MIssssLate

It works with or without the "end"

[parthsna]

why rk?

[samarpan88]

Thanks for uploading these tutorials.

It is a very nice way of learning matlab.

Because of these videos I got an A in my matlab examination.

Thanks again.

[andreselduro1978]

I apreciate it

[qbt8576]

Very helpful, I watched almost all videos you published, thanks very much for your great work.

[mayorga22]

very good tutorial.

when I solve the kdv equation, I impose for the equation to decay at both -inf and +inf.

how could I solve a similar problem that I change from a pde to a system of 2 odes.

I will like to impose that the function goes to zero at +inf.

I can bring the problem out of my old folders, if you can guide me on it.

thank you very much

[jakeblanchard]

I'm not familiar with the KdV equation. A quick Google search shows some approaches for reducing to an ODE. I can take a look at it, if you send me more details. Feel free to email me directly:

blanchard at engr "dot" wisc "dot" edu

[mayorga22]

lets forget about pdes.

I have 2 odes, a system of 2 odes that I want to solve in matlab, so I will get that equation and bring it to you, so that you can see it.

all I want to do is to the solution of the system of odes is to approach 0 as we move to postitive infinity.

hence the reason I ask about how to impose a certain condition to a solution solve in matlab, in this case is imposing that our solution goes to zero at positive infinity.

[jakeblanchard]

What if you solve them as a boundary value problem. Then you can force the solution to go to zero at some large value of x. Of course, you would have to give up on some initial condition. Interesting problem. I think you have the same problem with an analytical solution.

Send me specifics.

[uechanchung]

damn i cant believe i found this. haha good work man and thanks a bunch

[mekele7]

nice

[LTF85199]

Thank you ,thank you, thank you

[RaeRae17]

This is pretty cool, thank you!

[do7awi]

very useful :) thank you so much.

[aztellez]

Perfect explanation, helped me solve a nasty ODE for a Heat Transfer final project. Life saver!

[azharshah316]

good explanation. Thanks