What is Pdf: Definition and 345 Discussions

Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1993 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating systems. Based on the PostScript language, each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, vector graphics, raster images and other information needed to display it.
PDF was standardized as ISO 32000 in 2008. The last edition as ISO 32000-2:2020 was published in December 2020.
PDF files may contain a variety of content besides flat text and graphics including logical structuring elements, interactive elements such as annotations and form-fields, layers, rich media (including video content), and three-dimensional objects using U3D or PRC, and various other data formats. The PDF specification also provides for encryption and digital signatures, file attachments, and metadata to enable workflows requiring these features.

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  1. T

    What is the distribution of the sum of two random vectors?

    I am trying to derive the distribution for the sum of two random vectors, such that: \begin{align} X &= L_1 \cos \Theta_1 + L_2 \cos \Theta_2 \\ Y &= L_1 \sin \Theta_1 + L_2 \sin \Theta_2 \end{align} With: \begin{align} L_1 &\sim \mathcal{U}(0,m_1) \\ L_2 &\sim...
  2. T

    PDF of arccos and arcsin of a uniform random number

    Homework Statement I want to find the PDF for arccos and arcsin of a uniform random number. Given: Y\sim\mathcal{U}(0,2\pi) \\ X = cos(Y) The Attempt at a Solution I started with trying to find the CDF: \begin{align} F_X& = P(X \le x) \\ & = P(cos(Y) \le x) \\ & = P(Y \le arccos(x))...
  3. N

    What is the PDF of z where z = x-y

    Hello, I 'm trying to express the PDF of z (z ≥ 0) where z = x-y (and let x,y ≥ 0) Thank you in advance
  4. N

    How to generally express a shifted PDF ?

    Hello, i am trying to solve the following. Given a general PDF (i.e., fx(x), where x ≥ 0), how can i express the PDF of y = c x in terms of fx(x)? I think that goes like this: fy(y) = fx(y/c)/c, but i 'm not sure. Any help would be useful. Thanks in advance
  5. D

    Sony DPT-S1 Eink PDF Reader: Is It Available Yet?

    I just read that Sony wanted to sell the 13,3 eink pdf-reader DPT-S1 in Japan in December. Have they started already? Has anyone already hands on experience?
  6. M

    Expected Value (joint pdf)

    Homework Statement A machine consists of 2 components whose lifetimes are X and Y and have joint pdf, f(x,y)=1/50 w/ 0<x<10, 0<y<10,0<x+y<10 Calculate the expected value of X given Y=5. Homework Equations E[X|Y]= \int_{-inf}^{inf} x f(x,y)/f(y) dx The Attempt at a Solution...
  7. U

    How Does the Kinetic Theory of Gases Describe Particle Collisions?

    Hi guys, I'm studying the Kinetic Theory of gases from Pauli's book Vol. 3. Here he describes a section on the Mean free path, where the probability of two particles with speed v and v' colliding is described as:What is f(v,v') here? Is it the velocity distribution function? If so, isn't it...
  8. N

    How to evaluate an ordered conditional PDF ?

    Hello, i would like to evaluate the following PDF: Let x1 ≥ x2 ≥ ... ≥ xL. What is the PDF of xi (where 1 ≤ i < L), given that xL ≥ T (where T is a predetermined fixed value) ?? Any help would be useful. Thank you in advance
  9. C

    Random process of uniform- graphing and pdf

    Homework Statement Word for word of the problem: Let N (t, a) = At be a random process and A is the uniform continuous distribution (0, 3). (i) Sketch N(t, 1) and N(t, 2) as sample functions of t. (ii) Find the PDF of N(2, a) = 2A. Homework Equations A pdf is 1/3 for x in...
  10. T

    Finding the CDF from a PDF with absolute value function

    Homework Statement Find the CDF of f(x) = |\frac{x}{4}| if -2<x<2 \\ 0 otherwise Homework Equations The Attempt at a Solution I have to integrate the pdf and to do so, I have to split it into two parts \int_{-x}^{0}\frac{-t}{4}dt + \int_{0}{x}\frac{t}{4}dt integrating I get \frac{x^2}{8} +...
  11. N

    How to calculate a conditionally trancated PDF from an ordered set

    Hello, I am trying to evaluate the following condition: Let x_1 ≥ x_2 ≥ ... ≥ x_L and x_L ≥ y, where y is a fixed deterministic value. What is the conditional PDF of x_j (1 ≤ j ≤ L), given that x_L ≥ y ? (recall that i < L)Note that the conditional PDF of x_j, for the case when x_1 ≥ x_2 ≥...
  12. S

    LaTeX Adding an excel graph into a LaTeX pdf.

    How do I go about doing this? I'd like the graph to be fitted to the size of the page (A4) also, not just stuck on at the end in full size.
  13. M

    Can anyone make sense of these equations in this pdf

    i don't know if this is the right place for this but here is the link to the pdf file if you could figure out what its about that would be great http://arxiv.org/ftp/physics/papers/0003/0003044.pdf
  14. N

    MHB Unlock the Mystery of Tricky Joint PDF with Expert Tips | Attached Image

    Please refer to the attached image. How am I supposed to integrate this, it's impossible to find anything!
  15. N

    MHB Conditional PDF of this random variable

    the random variable X and Y have a joint PDF given by: $f_{x,y}(x,y) = \frac{1}{10}$, $(x,y)\in[-1,1] * [-2,2] \cup [1,2] * [-1,1]$ a) find the conditional PDF for $f_{y|x}(x,y)$ and $f_{x|y}(xy)$ and b) find E[X|Y], E[X] and Var[X|Y]. Use these to calculate var(X) for part a) I am unsure...
  16. N

    MHB PDF of X^2: General Method & Question Answered

    I just started this topic and have a question: For a positive continuous random variable X, write down the PDF of Y = X^2 in terms of the PDF of X. So; writing the PDF of X, I get P(0<X<∞) =integral from 0 to ∞ fx(x)dx Is this correct? For Y=X^2, wouldn't the pdf be the exact same thing...
  17. LeDragonian

    Nexus 7 & PDF Files: Improve Your Learning Experience!

    I currently have a great thirst for reading up all sorts of Mathematics/Physics textbook which I have obtained as PDF files on my Nexus 7. I currently use two apps to use to books. These apps are Adobe Reader, and aldiko. I feel like these apps aren't good enough for organizing and locating the...
  18. dexterdev

    Summation of random sequences and convolution in pdf domain?

    Hi all, I have an all time doubt here. We know that if r.v z = x + y where x and y are 2 random sequences having corresponding pdfs p(x) and p(y), the pdf of z, p(z) = convolution ( p(x),p(y) ). I have seen the derivation for the continuous case although not thorough how to prove it. I...
  19. Safinaz

    Higgs production and PDF

    Hi all, I try to calculate the Higgs production cross section by Mathematica using for example the formula in [arXiv:hep-ph/0503172]. The problem comes when I calculate " σ_0 " it's of order 10^-10 pb at mh = 125 GeV ( 3.57), then when I convolute with the parton distribution function to get...
  20. I

    Change of variables in conditional pdf

    Hello, I have a simple question regarding changing variables in a conditional distribution. I have two independent variables r \in \mathbb{R}, r>0 \\ t \in \mathbb{I}, t>0 where r is "rate" (can be any positive real number although most likely to be around 1) and t is "time" (positive...
  21. E

    Are random variables based on the same pmf or pdf always independent?

    Are they always independent from each other so that you can multiply their E[X] together to form another E[X] with the same distribution and pmf or pdf?
  22. M

    Checking PDF Expiration in Adobe Reader 9.5.5: A Simple Guide by Josh

    hey all! i have a pdf and i am wondering how to check if it expires. i am opening it in adobe reader 9.5.5 thanks for any reply! josh
  23. P

    Find marginal pdf given joint pdf (stats)

    Homework Statement Given joint pdf: f(x,y) = (2/(x2(x-1)))(y-(2x-1)/(x-1)) x>1, y>1 find marginal pdf fx(x) Homework Equations fx(x) = ∫f(x,y)dy, 0, ∞ The Attempt at a Solution fx(x) = ∫(2/(x2(x-1)))(y-(2x-1)/(x-1)) dy, 1, ∞ = [-2y(x/(1-x))/x3],1,∞ = undefined. stuck here
  24. N

    How to Automatically OCR PDF Files in a Given Folder?

    Can anyone recommend a method to have all pdf files in a given folder automatically OCR? My scanner saves files as pdf, but I would like them to be searchable. Thanks in advance.
  25. P

    Pdf of weighted uniform random variables

    Let x(1),...,x(N) all be independent uniformally distributed variables defined on (0,1), i.e. (x(1),...,x(N)) - U(0,1). Define the random variable y(i) = x(i)/(x(1)+...+x(N)) for all i=1,...,N. I’m looking for the pdf of the random variables y(1),…,y(N). Has anyone come across such random...
  26. jegues

    Program for printing a list of PDF files

    I am trying to figure out if it would be possible to develop simple program to preform the following task: If I have a list of drawing numbers contained within excel an file as such, 1-02632-M-07502 0002/03 1-02632-M-07502 0003/02 1-02632-M-07502 0004/08 1-02632-M-07502 0005/02...
  27. B

    Uniform pdf from difference of two stochastic variables?

    Hi, I'm trying to find a probability distribution (D) with the following property: Given two independent stochastic variables X1 and X2 from the distribution D, I want the difference Y=X1-X2 to have a uniform distribution (one the interval [0,1], say). I don't seem to be able to solve it...
  28. S

    Pdf of angle formed by two normal random variables

    Hi Everyone! I have two normally distributed random variables. One on the x axis, the other on the y axis, like a complex normal random variable. I'm trying to find the pdf of the angle between a fixed point on the x-y plane(let's say point 1,0) and the vector formed by combining the two...
  29. P

    Find P(X>4Y) given joint pdf

    Homework Statement Suppose X and Y have the joint probability density function: f(x,y) = x+4y, 0<y<x<1 f(x,y) = 0 otherwise Find P(X>4Y) Homework Equations The Attempt at a Solution I'm not sure how to do this. I've already found marginal pdf's for x and y.. although I...
  30. E

    Joint PDF of two continuous random variables

    Homework Statement The joint PDF (probability density function) ##p_{X,Y}(x,y)## of two continuous random variables by: $$ p_{X,Y}= Axy e^{-(x^2)}e^{\frac{-y^2}{2}}u(x)u(y)$$ a) find A b) Find ##p_X (x), \ p_{y}, \ p_{X|Y}(x|y), and \ p_{Y|X}(y|x)## Homework Equations The first...
  31. P

    What is the Marginal PDF of X?

    Homework Statement Let X and Y be random variables of the continuous type having the join p.d.f.: f(x,y) = 8xy, 0<=x<=y<=1 Find the marginal pdf's of X. Write your answer in terms of x. Find the marginal pdf's of X. Write your answer in terms of x. Homework Equations The...
  32. iVenky

    Autocorrelation function from PDF?

    What is the exact prodecure for finding out the auto correlation function Rxx(τ) for a given pdf? Is it possible at all to find out the auto correlation function from the pdf? If not then what is given usually when you find out the auto correlation function Rxx(τ)? Thanks
  33. dkotschessaa

    Finding the Probability Density Function of Y with Given Continuous PDF f(x)

    Homework Statement Let the random variable X have the continuous probability density function f(x). find the probability density function of Y= F(x) Homework Equations I *think* we are meant to use something like h(y) = f(g^{-1}(y)) * ((dg^{-1}(y)) /dy) (That is as good as I...
  34. F

    How Are CDF and PDF Related in Statistics?

    how are cdf and pdf related in statistics? please help i have a test tomorrow
  35. M

    Quantam Mechanic - Particle in a rigid one-d box (PDF)

    Homework Statement Write down and sketch the probability distribution for the second excited state (n=3) of a particle in a rigid box of length a. What are the probabilities of finding a particle in the intervals [0.50a, 0.51a] and [0.75a, 0.76a]? Homework Equations |ψ(x)|^2 =...
  36. J

    Good PDF Merger program or site?

    Hey guys. I need to merge about 7 PDF's but a few of them are about 80MB in size. I've tried a few good PDF pages from around the web but they all seem to have about 50MB in limit. Could anyone suggest me a good program that has no limitations to size of PDF's? Preferably free but if not...
  37. nomadreid

    P(x=mean) of normal PDF with low sigma - not allowed?

    P(x=mean) of normal PDF with low sigma -- not allowed? About the normal probability distribution: with formula P(X=x) = (1/(σ*sqrt(2π))*exp(-(x-μ)2/2σ2), what happens when you look at P(X=μ) if σ<(1/sqrt(2π))? You get P(X=μ)>1, an absurdity. What is going on? Second question is one about...
  38. M

    Converting html document to PDF

    Hello, I am trying to convert a .html file of my unofficial transcript so I can send it to REU programs because I am trying to get into an REU this summer. I've tried using the website converters and I always get an error. Is there any way to conver this for free? Or, can I PM it to...
  39. A

    Pdf and Coefficient of Kurtosis

    Homework Statement Let X and Y be two independent exponential random variables with a common rate parameter λ>0. Let W=X-Y. a)Find the pdf of W=X-Y b) Find the coefficient of kurtosis of W=X-Y Homework Equations f(x)=λe^(-λx) f(y)=λe^(-λy) f(x,y) = (λ^2)e^(-λ(x+y)) Kurtosis =...
  40. A

    Moment Generating Function Given pdf

    Homework Statement X is distributed exponentially with λa=2. Y is distributed exponentially with λb = 3. X and Y are independent. Let W=max(X,Y), the time until both persons catch their first fish. Let k be a positive integer. Find E(W^k). Also, find P{(1/3)<X/(X+Y)<(1/2)}...
  41. A

    Continuous Variable pdf from a cdf

    Homework Statement f X,Y(x,y) = (8 +xy^3)/64, if -1<x<1, -2<y<2 0, otherwise Find the probability density function of W = 2X+Y. Homework Equations F(w) = Pr{W≤w}=∫∫f(x,y)dxdy f(w) = d/dw F(w) The Attempt at a Solution I found the support of W to be -4<w<4 I...
  42. S

    PDF of an exponential distribution

    Homework Statement Hi! I'm trying to find the PDF of W = abs(X-λ), where X is an exponential R.V. with rate parameter λ>0. Homework Equations The PDF for an exponential distribution is ∫λe^(-λx)dx. Taking the derivative of a CDF will yield the PDF for that function (I'm aware there are...
  43. J

    Obtaining marginal PDFs from joint PDF

    Homework Statement Hi all, I'm looking at the joint pdf F(x,y) = (8+xy^3)/64) for -1<x<1 and -2<y<2 (A plot of it is here: https://www.wolframalpha.com/input/?i=%288%2Bxy%5E3%29%2F64+x+from+-1+to+1%2C+y+from+-2+to+2 ...sorry about the ugly url) and trying to find the marginal PDFs for X and...
  44. J

    Marginal PDF for Uniformly Distributed X and Y?

    Hi all, I'm looking at the joint pdf F(x,y) = (8+xy^3)/64) for -1<x<1 and -2<y<2 (A plot of it is here: https://www.wolframalpha.com/input/?i=%288%2Bxy%5E3%29%2F64+x+from+-1+to+1%2C+y+from+-2+to+2 ...sorry about the ugly url) and trying to find the marginal PDFs for X and Y. I know I want to...
  45. P

    Expected value and variance of a conditional pdf (I think I have it)

    Homework Statement Suppose the distribution of X2 conditional on X1=x1 is N(x1,x12), and that the marginal distribution of X1 is U(0,1). Find the mean and variance of X2. Homework Equations Theorem: E(X_{2})=E_{1}(E_{2|1}(X_{2}|X_{1}))...
  46. S

    Statistics Problem: finding a PDF using the CDF technique

    Hey guys, I'm stuck on a question in my homework assignment and I was wondering if you could push me in the right direction? So here's the question: X and Y are continuous random variables with joint pdf f(x,y)= 4xy (0<x<1, 0<y<1, and otherwise 0). Find the pdf of T=X+Y using the CDF...
  47. iVenky

    What is the pdf of multiplication of two random variables?

    We have two independent random variables X and Y whose pdfs are given as f(x) and f(y). Now when you multiply X and Y you get a random variable say Z. Now what is the resulting pdf f(z)? I mean how is that related to the pdf of f(x) and f(y)? From what I read it looks like f(z)=f(x) *...
  48. qspeechc

    LaTeX Pdf of Not So Short Intro to Latex

    Pdf of "Not So Short Intro to Latex" Hi everyone I'm trying to download "The Not So Short Introduction to LaTeX2e" by Oetiker, but every link I try I get the message "This webpage wants to run the following add-on: 'Zeon Corporation' from 'Zeon Corporation'." Then I am asked if I want to allow...
  49. C

    Finding a PDF Reader for E-Ink Displays: Updates & Suggestions

    I finally found out exactly what I'm looking for, the problem is, I can't find it anywhere. E-ink is best for the eyes, but it seems like there are no e-ink readers that can properly handle pdf-files. Kindles seem useless for pdfs and unfortunately Apple Ipad are hard on the eyes because of...
  50. dexterdev

    Why are there more zeros in a sine wave than 1s and -1s?

    Hello guys, From a layman's viewpoint when we count occurrences of different amplitude values, then frequency of zeros must be maximum is not it? but it is as below: why so? zeoros must be maximum, 1s and -1s are lesser than 0 isn't it?
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