# got stuck in equation

Discussion in 'Python' started by usamazohad@gmail.com, Jan 1, 2013.

1. ### Guest

hi . . my name is usama khan
i am the student of civil engeering and we got assignment to make a project program on flexible pavement design using python.

i know very litle about programing. still learning from tutorials. u can call me a beginner.
now i need to solve this equation so that i can put this in python but the formula of design is very complex

Formula is :

log(W18) = (Z)(S)+9.36log(SN+1) -2.0+(log(dpsi/(4.5-1.5))(/(.40+1094/(SN+1)^2.5)+2.32log(Mr-)-8.07

every thing is constant except this SN. . i want to seperate SN like SN= rest of the stuff. how can i seprate it because manualy its impossible to take SN out.
so plz help me out

, Jan 1, 2013

2. ### Chris AngelicoGuest

On Wed, Jan 2, 2013 at 2:40 AM, <> wrote:
> hi . . my name is usama khan
> i am the student of civil engeering and we got assignment to make a project program on flexible pavement design using python.
>
> i know very litle about programing. still learning from tutorials. u can call me a beginner.
> now i need to solve this equation so that i can put this in python but the formula of design is very complex
>
> Formula is :
>
> log(W18) = (Z)(S)+9.36log(SN+1) -2.0+(log(dpsi/(4.5-1.5))(/(.40+1094/(SN+1)^2.5)+2.32log(Mr-)-8.07
>
> every thing is constant except this SN. . i want to seperate SN like SN= rest of the stuff. how can i seprate it because manualy its impossible to take SN out.
> so plz help me out

This isn't a Python question, it's an algebra one. I don't know what
Z, S, and so on are, but for the most part, the basic rule of solving
equations applies: Do the same thing to both sides and it's still
true. Work on it until you can isolate SN on one side.

I don't know what this bit means, though:

2.32log(Mr-)

Is this a transcription error? You can't subtract nullness from something.

ChrisA

Chris Angelico, Jan 1, 2013

3. ### Dave AngelGuest

On 01/01/2013 10:40 AM, wrote:
> hi . . my name is usama khan
> i am the student of civil engeering and we got assignment to make a project program on flexible pavement design using python.
>
> i know very litle about programing. still learning from tutorials. u can call me a beginner.
> now i need to solve this equation so that i can put this in python but the formula of design is very complex
>
> Formula is :
>
> log(W18) = (Z)(S)+9.36log(SN+1) -2.0+(log(dpsi/(4.5-1.5))(/(.40+1094/(SN+1)^2.5)+2.32log(Mr-)-8.07
>
> every thing is constant except this SN. . i want to seperate SN like SN= rest of the stuff. how can i seprate it because manualy its impossible to take SN out.
> so plz help me out

Tk Solver is (or was) a program for getting numerical results from
equations where you couldn't (or didn't want to) express the equation
with the independent variable isolated on its own side of the equals
sign. I don't know where it's available for purchase or download now;
I do see references to it on the web, plus books still available about
it. Apparently it's up to version 5.

Anyway, since everything else is a constant, use some program like Tk
Solver to get the value for SN, then the Python program becomes simply:

SN = 4.7732

or whatever.

On the other hand, perhaps you didn't mean the other values were
constant, but rather known. For example, perhaps your program is
supposed to ask the user for values to W18, to dpsi, etc., then it is to
calculate one or more values for SN that make the equation work.

SN might be "structural number" as indicated on this web page:

http://classes.engr.oregonstate.edu/cce/winter2012/ce492/Modules/06_structural_design/06-3_body.htm

The big equation on that page looks kinda like the one you present,
though I didn't study every term.

1)
Is there a finite range of values that SN might fall into? I know
nothing about pavement design, other than what I just read there, but
there might well be a specific range that's reasonable to expect.

2)
Take the present equation, and subtract log(w18) from both sides. Now,
you want a value for SN that produces zero, or something close for the
left hand side. Call that side "error". Is the value "error"
relatively predictable for changes in SN ? For example, in the simplest
case, any increase in SN will result in an increase of error. The worst
case would be where any tiny change in SN might result in enormous
changes in a random direction to error.

3)
Figure an acceptable value for error, so you'll know when you're close
enough.

4)
if the first three questions have good answers, then you could write a
function that transforms FN into error. Then write a controlling loop
that calls that function repeatedly, picking values for FN that will
converge the error into ever-smaller value. The first iteration might
go over the entire range, dividing it into maybe ten steps. Then pick
the two smallest values for error, and treat those particular two FN

Repeat until the error value is below the threshold figured in #3, or
until you've iterated an unreasonable number of times.

There are ways to improve on that, but they generally require you know
the approximate behavior of the function. For example, Newton's method
is a method of calculating square roots, starting with end points of 1
and N, and it converges more rapidly because it effectively calculates
the slope of the curve over each range.

--

DaveA

Dave Angel, Jan 1, 2013
4. ### Dave AngelGuest

On 01/01/2013 11:03 AM, Chris Angelico wrote:
> On Wed, Jan 2, 2013 at 2:40 AM, <> wrote:
>> hi . . my name is usama khan
>> i am the student of civil engeering and we got assignment to make a project program on flexible pavement design using python.
>>
>> i know very litle about programing. still learning from tutorials. u can call me a beginner.
>> now i need to solve this equation so that i can put this in python but the formula of design is very complex
>>
>> Formula is :
>>
>> log(W18) = (Z)(S)+9.36log(SN+1) -2.0+(log(dpsi/(4.5-1.5))(/(.40+1094/(SN+1)^2.5)+2.32log(Mr-)-8.07
>>
>> every thing is constant except this SN. . i want to seperate SN like SN= rest of the stuff. how can i seprate it because manualy its impossible to take SN out.
>> so plz help me out

> This isn't a Python question, it's an algebra one. I don't know what
> Z, S, and so on are, but for the most part, the basic rule of solving
> equations applies: Do the same thing to both sides and it's still
> true. Work on it until you can isolate SN on one side.

Such a rule may not be able to solve an equation when there SN appears
more than once on the RHS, and where it's inside a transcental
function. I don't consider this an algebra problem, but a programming
problem.

> I don't know what this bit means, though:
>
> 2.32log(Mr-)
>
> Is this a transcription error? You can't subtract nullness from something.
>
> ChrisA

Mr- was apparently intended to mean "M sub r", the subgrade resilient
modulus
<http://classes.engr.oregonstate.edu/cce/winter2012/ce492/Modules/04_design_parameters/04-2_body.htm#mr> (in
psi). Just a number.

The only thing i know about any of this is from here:

http://classes.engr.oregonstate.edu/cce/winter2012/ce492/Modules/06_structural_design/06-3_body.htm

--

DaveA

Dave Angel, Jan 1, 2013
5. ### Usama KhanGuest

am just a begginer bro. . jus learnt if elif while nd for loop. .

can u just display me the coding u want. .it could save my time that i havewhile searchning SN out. . i will give u that dependable variables values.

Usama Khan, Jan 1, 2013
6. ### Usama KhanGuest

am just a begginer bro. . jus learnt if elif while nd for loop. .

can u just display me the coding u want. .it could save my time that i havewhile searchning SN out. . i will give u that dependable variables values.

Usama Khan, Jan 1, 2013
7. ### Usama KhanGuest

Usama Khan, Jan 1, 2013
8. ### Usama KhanGuest

Usama Khan, Jan 1, 2013
9. ### Chris AngelicoGuest

On Wed, Jan 2, 2013 at 3:42 AM, Dave Angel <> wrote:
> On 01/01/2013 11:03 AM, Chris Angelico wrote:
>> This isn't a Python question, it's an algebra one. I don't know what
>> Z, S, and so on are, but for the most part, the basic rule of solving
>> equations applies: Do the same thing to both sides and it's still
>> true. Work on it until you can isolate SN on one side.

>
> Such a rule may not be able to solve an equation when there SN appears
> more than once on the RHS, and where it's inside a transcental
> function. I don't consider this an algebra problem, but a programming
> problem.

It's a tad more complicated than your average equation, and I haven't
the time now to prove the point by actually solving it, but every
operation that I can see in that formula can be reversed. The hairy
bit is that there are two references to SN, so it's going to be a bit
messy to untangle, and might end up as a higher-order equation.

But you're likely right that other forms of solver may be more useful
here. Algebra definitely _could_ be the solution, but it isn't
necessarily the best.

ChrisA

Chris Angelico, Jan 1, 2013
10. ### Roy SmithGuest

In article <>,
Usama Khan <> wrote:

> am just a begginer bro.

That's fine, we were all beginners once. You will discover that people
here are willing to invest a lot of time and effort helping beginners
get started.

> now can u give me the coding of this equation as i need to save my time. . .i
> am learning from tutorials. . so its taking lot of time. kindly consider my
> request nd give me the code so that i can put it. .i dont want to losen up my
> grade. .am trying hard. . .

You will also discover that people are not willing to invest any effort
to help if you are not also willing to invest your own effort. Nobody
is going to just give you some code for your homework assignment so you
don't have to put any time into it.

Roy Smith, Jan 1, 2013
11. ### Chris AngelicoGuest

On Wed, Jan 2, 2013 at 4:25 AM, Usama Khan <> wrote:
> now can u give me the coding of this equation as i need to save my time. .. .i am learning from tutorials. . so its taking lot of time. kindly consider my request nd give me the code so that i can put it. .i dont want to losen up my grade. .am trying hard. . .

work for you. You haven't said what sort of class this is, but I see
two likely possibilities:

1) It's a programming class. Either you ought to be able to solve this
in the class (in which case, look to your source material as it's
almost certainly there - this is way more complicated maths than your
average programming class wants as an ancillary), or you shouldn't be
doing this part at all, and you can achieve the program's goal without
actually running the maths.

2) It's a course on something else (engineering?), to which this
formula is central. Then you ought to understand the mathematics of
it, regardless of the code.

Either way, posting urgent messages to python-list asking for someone
to *give you the code* is NOT the way to do things. We'll help you to
plenty of Q'n'A web sites out there with low standards and no
scruples, but please just make sure you never build a bridge that I'll
be travelling over.

Read this, it'll help explain what people think of these sorts of questions:
http://www.catb.org/esr/faqs/smart-questions.html#homework

ChrisA

Chris Angelico, Jan 1, 2013
12. ### Usama KhanGuest

u r right bro. . am serving my time. .realy i dont need a short cut code. .

nor its a programing class. .
i have chosen tis project on my own so that we can aviod that graph procedure. .

i guess the program i am making on python has many many things. .not just the iteration. .i am not that cheap really to cheat my DS(director of studies). .i swear. .

as i told i am half civil engieer. .in 5 th semester presently. .

am ready to learn. . .still learning from tutorialz of "tekboi" and "investros" and that book name "python programing for absolute begginers"

kindly understand me. .i can give u my time. .u got me wrong. i just ask for the coding of solving this formula as its not in the book as well as tutorialz.

thanks for the concern. .
regards

Usama Khan, Jan 1, 2013
13. ### Usama KhanGuest

u r right bro. . am serving my time. .realy i dont need a short cut code. .

nor its a programing class. .
i have chosen tis project on my own so that we can aviod that graph procedure. .

i guess the program i am making on python has many many things. .not just the iteration. .i am not that cheap really to cheat my DS(director of studies). .i swear. .

as i told i am half civil engieer. .in 5 th semester presently. .

am ready to learn. . .still learning from tutorialz of "tekboi" and "investros" and that book name "python programing for absolute begginers"

kindly understand me. .i can give u my time. .u got me wrong. i just ask for the coding of solving this formula as its not in the book as well as tutorialz.

thanks for the concern. .
regards

Usama Khan, Jan 1, 2013
14. ### Usama KhanGuest

how shud i intiate this equation myself. .can u give me some links to solvethat myself. . am ready already. .its a chalange for me now. . .i just requested for a code as i dont know nothing about iteration of that much complex equation not the entire program. .

so kindly show me the way. .i will do it myself. .nd remember plz am nt that cheap to cheat. .cheater doesnot worry about grades. .just remember this..he just wants to clear the subject. . i have cleared the subject with excellent marks. .just spoiling my end semester vacation to get good grade andexpereince in programing. . . its totaly optional to go for project, internship or vacationz. .nd i have chosen up the project. . .i hope i have clearified your doubt regarding my amnitions and concerns. . ??

so kindly show me the way. .i will go myself on that way. .because i dont know what way should go for this beautiful complex equatuion. .

Usama Khan, Jan 1, 2013
15. ### Usama KhanGuest

how shud i intiate this equation myself. .can u give me some links to solvethat myself. . am ready already. .its a chalange for me now. . .i just requested for a code as i dont know nothing about iteration of that much complex equation not the entire program. .

so kindly show me the way. .i will do it myself. .nd remember plz am nt that cheap to cheat. .cheater doesnot worry about grades. .just remember this..he just wants to clear the subject. . i have cleared the subject with excellent marks. .just spoiling my end semester vacation to get good grade andexpereince in programing. . . its totaly optional to go for project, internship or vacationz. .nd i have chosen up the project. . .i hope i have clearified your doubt regarding my amnitions and concerns. . ??

so kindly show me the way. .i will go myself on that way. .because i dont know what way should go for this beautiful complex equatuion. .

Usama Khan, Jan 1, 2013
16. ### Ramchandra ApteGuest

On Tuesday, 1 January 2013 22:55:21 UTC+5:30, Usama Khan wrote:
> am just a begginer bro. . jus learnt if elif while nd for loop. .
>
>
>
> can u just display me the coding u want. .it could save my time that i have while searchning SN out. . i will give u that dependable variables values. .
>
>
>
> nd SN range 4 inches to 13.5 inches
>
>
>
> log(w18)=50x10^6
>
> Z=-1.645
>
> S=0.45
>
> dpsi=2.5
>
> Mr=5800
>
>
>
> now can u give me the coding of this equation as i need to save my time. .. .i am learning from tutorials. . so its taking lot of time. kindly consider my request nd give me the code so that i can put it. .i dont want to losen up my grade. .am trying hard. . .
>
>
>
> Regards

If you spend half a minute extra to write your sentences properly and not use SMS abbreviations, then it would save totally many minutes of other people's time.

Ramchandra Apte, Jan 2, 2013
17. ### Ramchandra ApteGuest

On Tuesday, 1 January 2013 22:55:21 UTC+5:30, Usama Khan wrote:
> am just a begginer bro. . jus learnt if elif while nd for loop. .
>
>
>
> can u just display me the coding u want. .it could save my time that i have while searchning SN out. . i will give u that dependable variables values. .
>
>
>
> nd SN range 4 inches to 13.5 inches
>
>
>
> log(w18)=50x10^6
>
> Z=-1.645
>
> S=0.45
>
> dpsi=2.5
>
> Mr=5800
>
>
>
> now can u give me the coding of this equation as i need to save my time. .. .i am learning from tutorials. . so its taking lot of time. kindly consider my request nd give me the code so that i can put it. .i dont want to losen up my grade. .am trying hard. . .
>
>
>
> Regards

If you spend half a minute extra to write your sentences properly and not use SMS abbreviations, then it would save totally many minutes of other people's time.

Ramchandra Apte, Jan 2, 2013
18. ### alex23Guest

On Jan 2, 3:20 pm, Ramchandra Apte <> wrote:
> If you spend half a minute extra to write your sentences properly
> and not use SMS abbreviations, then it would save totally many
> minutes of other people's time.

But that is not the way of the brogrammer...

alex23, Jan 2, 2013
19. ### DJCGuest

On 02/01/13 05:20, Ramchandra Apte wrote:
> On Tuesday, 1 January 2013 22:55:21 UTC+5:30, Usama Khan wrote:
>> am just a begginer bro. . jus learnt if elif while nd for loop. .
>> can u just display me the coding u want. .it could save my time that i have while searchning SN out. . i will give u that dependable variables values. .
>> now can u give me the coding of this equation as i need to save my time. .. .i am learning from tutorials. . so its taking lot of time. kindly consider my request nd give me the code so that i can put it. .i dont want to losen up my grade. .am trying hard. . .

> If you spend half a minute extra to write your sentences properly and not use SMS abbreviations, then it would save totally many minutes of other people's time.

+1 not to mention that a polite, respectful, and well written request
might incline more people to offer help.

DJC, Jan 2, 2013