Physics Forums - Math & Science Software

Strikethrough in latex

Pranav-Arora — Tue, 14 May 2013 12:05:44 GMT

Is it somehow possible to do it in LATEX? I googled it but I couldn't find anything that would work for me.

Looking for free online integration calculator.

yungman — Mon, 13 May 2013 17:05:40 GMT

I have been looking for an integration calculator. I need to solve

[tex]\int_0^{\pi} \frac{\cos (a \cos \theta)}{\sin \theta} d\theta[/tex]

This is a sine integral that likely involve numerical analysis. I tried Wolfram free Mathematica and it did not find a solution. Please advice.

How to correctly code the expression with Ei function?

Ein Krieger — Sun, 12 May 2013 04:17:53 GMT

Hi,

I am trying to incorporate the following equation into Matlab in the red:

The following data is to be used:
t=3000000
nr=nx=161
q=0.02
k=5e-13
mu=0.00035
c=1.5e-8
phi=0.25
rw=0.1
h=4.5

My code is below:
st=size(t)
nr=nx;
for i=1:1:st(1)
rd=r(1:nr)/wb
td=0.0036*k*t(i)/(phi*mu*c*wb^2)
pd=((pi*h*k)/(1.842*q*1.1*mu))*(IP-p(i,1:nr))
Ei_from_mfun=mfun('Ei',1,-rd^2/(4*td))
pd=1/2*Ei_from_mfun
plot(time,pd,'bo')
end

But it gives the following command :
"??? Index exceeds matrix dimensions."

Can you please help to fix the problem for every time, t and pressure,p?

Thanks

[Matlab] Transform generated table to equation for for loop usage

roldy — Sat, 11 May 2013 08:44:13 GMT

I have posted a question on here before regarding the generation of a number sequence. I followed up that question with an answer. However, as I have developed my code more I need to use an equation instead of a lookup table.

Note: I'm using MATLAB

Given a matrix A of size r x c where r >= 3, c >= 3 I need to map the center point of a 3 x 3 raster segment to a point in A. The raster segments go from left to right, top to bottom. For example, if

Code:

A = [0 1 1 0 1 0 1 0 1;...

      0 0 1 0 0 1 1 0 1;...

      1 0 1 1 0 1 0 1 0;...

      1 1 1 1 1 1 1 1 1];...

The location of (2,2) in each raster segment can be found as follows.

Code:

%raster binary image matrix into 3x3 segments

M = im2col(FP, [3,3],'sliding');



[ri ci] = size(A);

[rM cM] = size(M);



%Generate table of locations in binary image matrix for center point (2,2) of segment matrices

rownums = repmat([2:ri-1],cM/(ri-2),1);

rownums = rownums(:);



colnums = repmat([2:ci-1]',1,cM/(ci-2));

colnums = colnums(:);



locations = [rownums,colnums]

I only need matrix M to find what rM and cM are. Instead of using the im2col() function, I can use the equations below. cM is the number of total raster segments

Code:

rM = 9;

cM = (ci-2)*(ri-2);

I do some matrix operations for each raster segment using a for loop

Code:

n = 1;



k = 1; 

for row = 1:ri-2

 

        for col = 1:ci-2

  

           %some operations

                

                if %condition is met

                    %transform center point location in raster segment

                    %to corresponding location in matrix A

                    Iloc(n,:) = locations(k,:);

                    n = n+1; 

                end

            

            else   %if condition is not met, increment segment counter k and continue

                    %in for loop to next segment

                k = k+1;

                continue

            end

        k = k+1;

        end

        

end

I would like to replace this line of code

Code:

Iloc(n,:) = locations(k,:);

with equations for the row and column location in A instead of looking up in the table for these locations. The reason for this is that if I have a matrix A of size 274 x 234, I would have 63104 raster segments. This means that my location table matrix would be 63104 x 2. This takes up a lot of memory with the other stuff that I am doing. I know it's possible to come up with some equation that's dependent on the value of row, col, and k. It seems that every (ci-2) kth value, the row in A increments by one. For every different row value, the column values go from 2:(ci-1).
Question is how do I activate the row increment and column range for every (ci-2) kth value?

Extract and rearrange data in Matlab

geoffrey g — Fri, 10 May 2013 20:34:17 GMT

Hi all,

I need to rearrange my data. I have an excel file with 12 columns and 2045 rows, which I transformed that into a .mat.

I need to query my data rearranged as follows (cf. example matrix below):

1-sum all values of Col 3 if:
a-they belong to a given value of Col 1 and to a given value in Col 2.
2-mean of values of Col 4 for each given value of Col 1

3-NaN's where conditions above are not met
4-all saved in a new matrix

The difficulty is to make this work for the 2045 rows of my database. I guess it needs a for-loop that reiterates the calculations and at each step saves the values in a matrix.

Here is an example:

input matrix A:

1 NaN NaN 20
1 2 4 10
1 2 3 15
1 NaN NaN 10
1 5 2 25
1 6 1 10
1 2 5 5
2 NaN NaN 5
2 1 3 10
2 1 2 25
3 6 5 15
3 4 3 10
3 3 1 30

This is what I'd like to get:

1 2 3 4 5 6 Mean
1 NaN 12 NaN NaN 2 1 13.57
2 5 NaN NaN NaN NaN NaN 13.33
3 NaN NaN 1 3 NaN 5 18.33

I'd really appreciate your help and will include you in the acknowledgments of the 2 papers I will get out of this.

Thanks a lot!!

g

How to simulate 2nd order markov chain (if poss. Nth order) in MATLAB

dexterdev — Fri, 10 May 2013 15:35:41 GMT

Hi PF,
I would like to simulate N th order markov chain (not by means of hidden markov models, but ordinary markov chain) using Matlab. If n-th order is a heavy thing atleast 2nd or 3rd order will do.

TIA

How to do this vector operation in MATLAB ?

dexterdev — Fri, 10 May 2013 15:30:14 GMT

Hi friends,
I wanted a help in Matlab programming. I have some vectors as below :

d4=cos(2*pi*293.665*(0:1/44100:.25));
f4=cos(2*pi*349.228*(0:1/44100:.25));
e4=cos(2*pi*329.628*(0:1/44100:.25));
g4=cos(2*pi*391.995*(0:1/44100:.25));
c5=cos(2*pi*523.251*(0:1/44100:.25));
bb4=cos(2*pi*466.164*(0:1/44100:.25));
a4=cos(2*pi*440*(0:1/44100:.25));
c4=cos(2*pi*261.626*(0:1/44100:.25));

and finally a vector x build from the above vectors :

x=[c4 c4 d4 c4 f4 e4 c4 c4 d4 c4 g4 f4 c4 c4 c5 a4 f4 e4 d4 bb4 bb4 a4 f4 g4 f4];

here a4 must be assigned 1, bb4 - 2, c4 - 3, d4 - 5, e4 - 6 , f4 - 7 and g4 - 8. I wanted to create a vector y from x. y must be as below :

y = [3 3 5 3 7 6 3 3 5 3 8 7 3 3 4 1 7 6 5 2 2 1 7 8 7] ;

TIA

LaTex: Where to store package, sty, etc files?

teroenza — Fri, 10 May 2013 14:18:04 GMT

Hello. I am using windows 7, MikTex, and Texmaker to create LaTeX files. I am a novice user, and am confused about where to locate specific files such as packages, .sty files, and .cl files. I use MikTex's package manager to download most, and it puts them somewhere where they are then accessible for any document I create. If it can't find what need (as indicated by an error in Texmaker), then I manually find the file online and stick it in the folder with the .txt file. Is there a place I can put these files so that I don't have to have a copy with every .txt document I have?

Thanks

[Mathematica] Simple Problem with the plot function

PEZenfuego — Thu, 09 May 2013 00:57:33 GMT

I have a formula for the fibonacci sequence (with 1 being the first) and I noticed that the 12th fibonacci number was 144. I thought that was a neat coincidence, so I I headed over to mathematica to see if this (and 1) were the only numbers that had this property. I was almost certain that it was. So I plotted the two graphs, but only the x^2 graphed showed up. Here was my input. My question is about what I did wrong.

phi := (1 + Sqrt[5])/2

phih := (1 - Sqrt[5])/2

f:={(phi^n)-(phih^n)}/{Sqrt[5]}

y:=n^2

Plot[{f, y}, {n, -20, 20}]

Now, this works when I remove the phih term, which works well enough that I can clearly see that only 1 and 12 are solutions. On the other hand, this is not plotting something that it should be plotting...

Anyway, thank you in advance for the help.

Problems with mathematica code

johalia — Wed, 08 May 2013 19:08:48 GMT

Hello!

I'm writing a paper where I'm going to use markov models to evalute a device. My base for this paper is the paper written by H. Timbley. I have never used Mathematica before and thought that I would start by trying the complete code that Timbley has written in the appendix of the paper. The code is:

DiscreteMath`Combinatorica`;
IndexOf[vector , e ] := Position[vector, e][[1, 1]];

device =
{{"Clock", "Clock", "Clock", "Clock", "Clock", "Clock"},
{"Quick Defrost", "Quick Defrost", "Quick Defrost",
"Quick Defrost", "Quick Defrost", "Quick Defrost"},
{"Timer1", "Timer1", "Timer2", "Timer1", "Timer2", "Timer1"},
{"Clock", "Clock", "Clock", "Clock", "Clock", "Clock"},
{"Clock", "Quick Defrost", "Power1",
"Power2", "Power1", "Power2"}
};

buttonNames = {"Clock", "Quick Defrost", "Time", "Clear", "Power"};
stateNames = {"Clock", "Quick Defrost", "Timer1", "Timer2", "Power1",
"Power2"};

numberOfStates = Length@stateNames;
numberOfButtons = Length@buttonNames;

start = IndexOf[stateNames, "Power1"];
goal = IndexOf[stateNames, "Power2"];

Until then the code work just fine, but when I type in the next section described in the appendix (see below), some error codes pop up.

Do[randomUser[[i, IndexOf[stateNames, device[[b, i]]]]] +=
1/numberOfButtons, {b, numberOfButtons}, {i, numberOfStates}];

Error codes:
Part::partw: Part 1 of {} does not exist. >>
Part::pspec: Part specification {}[[1,1]] is neither a machine-sized integer nor a list of machine-sized integers. >>
Part::partw: Part 1 of {} does not exist. >>
Set::pspec: Part specification {}[[1,1]] is neither a machine-sized integer nor a list of machine-sized integers. >>
Part::partw: Part 3 of {Quick Defrost,(Quick Defrost)^5} does not exist. >>
General::stop: Further output of Part::partw will be suppressed during this calculation. >>
Part::pspec: Part specification {}[[1,1]] is neither a machine-sized integer nor a list of machine-sized integers. >>
Set::pspec: Part specification {}[[1,1]] is neither a machine-sized integer nor a list of machine-sized integers. >>
Part::pspec: Part specification {}[[1,1]] is neither a machine-sized integer nor a list of machine-sized integers. >>
General::stop: Further output of Part::pspec will be suppressed during this calculation. >>
Set::pspec: Part specification {}[[1,1]] is neither a machine-sized integer nor a list of machine-sized integers. >>
General::stop: Further output of Set::pspec will be suppressed during this calculation. >>

Is there anybody that could tell me what's wrong with the code?

Minimal Programming Mathematics Software

Alexrey — Wed, 08 May 2013 08:21:49 GMT

After using Matlab here and there whilst I was at university, I thought that although it was very powerful, its use was extremely cumbersome and slowed down what should be fairly simple processes like making 3D plots and solving ODEs, PDEs etc. That got me wondering if there were any programs out there that take out as much of the programming as possible and let you focus more on the mathematics. So if I decided to, say, solve the 2D wave equation and create a time varying 3D plot of the result, it wouldn't take me more than 5 minutes.

Are there any programs out there that allow someone to do that?

How do I plot this periodic step function with GNUplot?

randombill — Mon, 06 May 2013 21:07:38 GMT

[tex]\sum_{k=0}^{∞} (t-2k) [u(t-2k)-u(t-2(k+1))] = f(t)[/tex]

where [tex]u[/tex] is the step function and the graph of this is supposed to be 45 degree lines repeating to infinity. Sort of like

/ / / / / / / / / ad infinitum. I took this equation out of this lecture note on page 10. Fig 5.4 is supposedly the graph of it and example 5.27 is where they ask to solve it.

How to display all calculation results in Matlab

Ein Krieger — Mon, 06 May 2013 17:46:03 GMT

Hi,

How can I set Matlab to display all the calculation results?

I am solving the system of ODEs with large spatial variable and time step distribution. If I set total time to 100 with time step of 1 only the results starting from t=50 are displayed.

How to fix it?:frown:

Thanks.

How to convert GO TO (Fortran77) to Matlab

Triscas — Mon, 06 May 2013 10:28:04 GMT

I'm translating some code from Fortran77 to Matlab and I'm struggling due to the sentence GO TO is not valid in Matlab.
Usually using sentences while I can solve the problem but in a particular case I don't know how to face it.
To put in situation, i.e:

code
line 1
line 2
...
128 a=a+1

if c==1 && kcount < 20 then
line
line
if (h < 30) then
go to 128
end if
end if
line
line
if (zmax == 0) go to 128
if (zmin. lt. 0.999d0*zmax) go to 128
line
end

The problem, if can be apreciated, is the go to inside the double if statement that also is in normal if statements.

If it's neccesary I could write the code.

Thanks!

Any physics simulation software?

s0ft — Mon, 06 May 2013 05:05:00 GMT

Is there any software for simulating physical phenomena?
I've googled it and found one named Physion.
It is great for fun but is too limited.
Would programming be the only way or is there some ready-made program that could provide an easy environment to develop simulations.