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. E

    Solving PDF with set boundary values

    I am give probability distribution function f(x)=(e(-x/1000))/1000 of the time to failure of an electronic component in a copier The question is to determine the number of hours at which 10% of all components have failed. My solution: 1) PDF was integrated to obtain: f(x)= e(-x/1000)...
  2. dexterdev

    Get Frequency Distribution Vector from a Random Sequence

    Hi all, suppose I have a random discrete sequence like x= [1 2 3 2 5 2 4 2 3 1 6 3 5] (where possible outcomes are 1,2,3,4,5 or 6) and wanted to get its frequency distribution vector f=[2 4 3 1 2 1] which means frequency of occurrence of 1 is 2 times, 2 occurs 4 times , and so on. I...
  3. N

    How to find the expected value of a continuous variable with pdf fy= y^(-2)?

    Homework Statement Find the expected value of a continuous variable y with pdf fy= alpha*y^-2, 0<y<infinity. I know it is the integral from zero to infinity of y*fy, but I don't know where to go from there. I'm then supposed to use the expected value to find the method of moments...
  4. P

    10 Calculus Questions Integrals,Equations, PDF file, Dead line after 1 hour

    Uploaded a pdf file My Answers : 1: a- x= 1/10 (9-√41) ≈0.259688,Or x=1/10 (9+√41)≈1.54031 b:y=0 Or y=7/3 c: didn't solve. d: t= 1/3 log⁡(5/2)≈0.30543 e::β=3/5 Or β=-3/5 2: didn't solve. 3:sin^-1⁡(√5/4)≈0.59 tan (0.59)≈0.67 4: didn't solve 5:sin⁡(α)+cos⁡(α)=4/3 We...
  5. B

    Probablity question (confused on the pdf)

    Homework Statement [itex] $f(x)=\begin{cases} 7(4)^{-i} & x\in(\frac{1}{2^{i}},\frac{1}{2^{i-1}}],i=1,2,3,...\\ 0 & 0\geq x,x>1 \end{cases}$ (please excuse the poor latex) Homework Equations The Attempt at a Solution the problem I'm having is say x=3/4. then according to the pdf...
  6. C

    Finding the pdf of a random variable which is a function of another rv

    Homework Statement Let f(x)=x/8 be the density of X on [0,4], zero elsewhere. a) Show that f(x) is a valid density and compute E(X) b) Define Y=1/X. Calculate E(Y) c) Determine the density function for Y The Attempt at a Solution a) is just really basic. I've solved that one. b)...
  7. S

    Best portable device for math PDF files?

    What's the best portable device for reading mathematical PDF files? - one that would show equations and graphs clearly? I'm not particularly interested in the general field of electronic books or wireless connectivity, but It would be nice to have portable device for the many free math PDFs...
  8. DeusAbscondus

    MHB Simple limit question in attached pdf

    Hello, I have a simple question regarding limits. I have attached this question as a pdf for reasons of accuracy (i can latex to pdf but haven't learned how to work with Mathjax directly here) Regs, DeusAbs
  9. J

    Mathematica Mathematica: Problem Computing Fisher Information of pdf

    Hello, I'm trying to calculate Fisher information (and eventually the Cramer-Rao lower bound) for this particular pdf with Mathematica: \text{pte}[t,\Theta ] = \frac{P_{\text{ec}}}{\tau _d-\tau _r}\left[e^{\frac{-(t-\Theta )}{\tau _d}}-e^{\frac{-(t-\Theta )}{\tau _r}}\right]...
  10. D

    Understanding Conditional PDFs: Exploring the Relationship between x1 and x2

    Hi, all. I happened to think about a problem about conditional PDF: x_2=x_1+a, x_1 \approx \mathcal{N}(0,1), a \approx \mathcal{N}(0,1) so the conditional PDF of f(x_2|x_1), f(x_1|x_2) would both be f(x_2|x_1)=f(x_1|x_2)=\frac{1}{\sqrt{2\pi}}\exp{(-\frac{(x_1-x_2)^2}{2})} And it is clear...
  11. Y

    Any safe free software to convert Word to PDF?

    Any suggestion on a free program to convert Word to PDF. I was playing around and I got malware that I am still trying to clean up. Thanks
  12. Y

    Transform Word Doc to PDF and PDF to Word Doc.

    Hi I am looking for free software that can transform Word Doc to PDF. Maybe PDF back to Word Doc. Any suggestion on which one is good? Thanks Alan
  13. F

    Finding covariance using the joint pdf

    The following question appeared on a practice exam: For f(x,y) = 24xy if 0<x+y<1 , 0<x,y 0 elsewhere find Cov(X,Y) I used Cov(X,Y) = E(XY) - E(X)E(Y) to calculate covariance, with E(XY) = \int^{1}_{0}\int^{1-y}_{0}24x^{2}y^{2}dxdy but for some reason I didn't get the...
  14. J

    Can I convert pdf documents into word just using adobe?

    I'm writting my paper and need to extract some paragraph out of pdf materials, but the pdf can not be copied, so I need to convert them to word so that I can edit the text. They said pdf can be saved as word document using adobe so I don’t have to use another tool, but I have no idea how to...
  15. E

    CDF and PDF of order statistics

    Hi, I have K i.i.d. exponentially distributed random variables with mean unity. I need to find the CDF and PDF of the summation of the largest two random variables. How can I do that? The problem in this case is that the combinations are not independent. Thanks in advance
  16. X

    Statistics: Using a PDF function

    Homework Statement I am doing a practice final exam in preparation of my actual final exam next week. Here is the link. I am doing problem number 2. http://www.math.stevens.edu/~ifloresc/Teaching/2011-2012/MA222S12/Final_Exam_Summer2011.pdf The Attempt at a Solution So this seems...
  17. J

    CDF of a variable with a negative exponent in its PDF

    Ok, this one's got me stumped! Let's take as an example the probability density function for a random variable X so that: f(x) = \frac{4}{3x^{3}} 1≤x<2 f(x) = \frac{x}{12} 2≤x≤4 f(x) = 0 So the CDF for this variable comes out as: F(x) = \frac{-2}{3x^{2}} 1≤x<2 F(x) =...
  18. R

    How do I graph and integrate a joint PDF with multiple inequalities?

    Homework Statement Find λ given that the joint PDF of random variables X, Y, is given by: f(x,y)=\lambda x y^{2} where 0\leq x\leq y\leq 1 and 0 otherwise I have two questions: 1) How do I graph this? I'm not sure how to approach the inequality and graphing. What does this inequality...
  19. N

    Mathematica Mathematica: Random numbers from arbitrary PDF

    Hi I want to generate a set of random numbers according to a specific distribution, namely given by f(v) \propto v^3\exp(-v^2 C) where C is a constant. It is clear how to do it with a distribution already implemented in Mathematica...
  20. L

    Problem with deriving joint/marginal PDF

    Hi, I'm having a problem with a MATLAB assignment in my probability class. It has to do with finding the joint and marginal PDFs of a pair of random variables. I understand this stuff on paper, but for some reason this assignment is giving me problems since I don't have a good idea of how the...
  21. E

    How Can I find the PDF of This?

    Hi, I have this random variable: Z=\left(\sum_{m=1}^NX_m^{-1}\right)^{-1} where Xm are i.i.d. exponential random variables with parameter 1, i.e. the PDF of these random variables is: f_{X_m}(x)=e^{-x} How can I find the CDF, PDF, and the MGF of Z? Thanks
  22. S

    Joint pdf question and mgf

    Hi guys, I'm really stuck on the following questions, not sure as to how to approach it: Let X and Y be random variables for which the joint pdf is as follows: f(x,y) = 2(x+y) for 0 <= x <= y <= 1 and 0 otherwise. Find the pdf of Z = X + Y And also: Suppose that X is a random variable for...
  23. R

    Expectation of a Function of a RV in terms of PDF

    Homework Statement Find the expected value of cos(A+B) where A is a constant and B is a random variable with a pdf f(b). Present the answer in terms of f(b). The Attempt at a Solution I don't know how far I can go with the answer -- I have tried for a bit now to remove an integral with no...
  24. F

    Free PDF Editor: Rotate & Delete Pages?

    One document I need to rotate by 180° and another I need to delete every other page (don't ask), is this possible with any free editing software? Thanks Dan
  25. D

    Obtaining a normalized PDF from a histogram?

    Suppose I have a regular histogram, I can normalize it by dividing the frequency counts by the total number of counts (at least I believe that's all you need to do). What you're left with should be an approximation to the underlying PDF (probability density function). What I'm asking is how...
  26. L

    Putting pdf science textbooks with equations on to a Kindle accurately

    Hi guys, I'm trying to put pdf science textbooks on to a kindle. They have difficult equations and subscripts/superscripts and pictures of atoms and things which however I try seem to become a jumble. So far I have tried: 1. Using Calibre - dodgy results, equations handled very badly 2...
  27. K

    Deriving the second raw moment of the rice PDF

    (the following is Mathematica code) For the rice pdf... P(x)=(x/σ^2) BesselI[0, x (ν/σ^2)] Exp[-(x^2 + ν^2)/(2 σ^2)] ...the Second raw moment is given by doing the integral... Integrate[(x^3/σ^2) BesselI[0, x (ν/σ^2)] Exp[-(x^2 + ν^2)/(2 σ^2)], {x, 0, Infinity}] While the answer...
  28. A

    PDF of Matrix Transformation

    Homework Statement Define X to be an n-vector of jointly continuous random variables X1, ..., Xn with joint pdf f(x) mapping R^n to R. Let A be an invertible nxn matrix and set Y=AX+b. I want to derive the pdf of f(y) in terms of f(x), the original pdf. Homework Equations The...
  29. A

    Penny flipped and uniform PDF generated

    Homework Statement A penny is flipped until we see the first head, and flips are assumed to be independent. For each tail we observe before the first head, the value of a continuous random variable with uniform PDF over the interval [0,3] is generated. Let the RV X be the sum of all the...
  30. D

    LaTeX Efficient Latex Wrapping: Avoiding PDF Overflow | Formula Included

    How can I get this to not wrap outside of my pdf $ \left(-\frac{1}{6 a}(-2 a (-2 + k) + \frac{2\ 2^{1/3} a \left(-3 + a (1 + k)^2\right)}{\left(9 a^2 (-2 + k)-2 a^3 (1 + k)^3 + 3 \sqrt{3} \sqrt{a^3 \left(4 + 4 a^2 (1 + k)^3-a \left(-8 + 20 k + k^2\right)\right)}\right)^{1/3}} + 2^{2/3} \left(9...
  31. E

    Finding the pdf of the average of n independent random variables

    Homework Statement The n random variables X_{1}, X_{2},..., X_{n} are mutually independent and distributed with the probability density f(x)=\frac{1}{\pi(1+x^{2})} i) Find the probability density of the average Y=\frac{1}{n}\Sigma^{i=1}_{n}X_{i} ii) Explain why it does not converge...
  32. M

    MHB Solving Linear First Order ODEs: y' + p(x)y = q(x)

    Given $u_t+u_x\cos t=u.$ a) Find the solution with $u(x,0)=f(x).$ b) If $f(x)=\left\{\begin{array}{cl}\cos^2x,&\text{if }-\frac\pi2\le x\le\frac\pi2,\\ 0,&\text{in the rest}.\end{array}\right.$ Describe $u(x,t)$ for $t\ge0.$ I have to use Fourier transform, but don't know how to apply it for...
  33. M

    MHB Solving PDF by using Fourier transform

    $u_t-u_{xx}=0,$ $x\in\mathbb R,$ $t>0$ and $u(x,0)=e^{-x^2}.$ By applying Fourier transform on $t$ I have $\dfrac{\partial }{\partial t}F(u)+{{\omega }^{2}}F(u)=0,$ the solution of the latter equation is $F(u)(\omega,t)=ce^{-\omega^2t},$ now by applying the initial condition I have...
  34. S

    PDF eReader for Journals? Two-Column Format?

    Let me start out and say I'm cheap so I would prefer not to buy an iPad or a Samsung Galaxy tablet. I'm looking for an eReader that does okay on reading the two-column scientific journal format. I don't care about any other features, battery life, etc. I've read people complain about all...
  35. G

    Normal Distribution: PDF of a Normally Distributed Random Variable

    Homework Statement A Normally distributed random variable with mean μ has a probability density function given by _ρ_...*...((-ρ2(x-μ)2)/2δ) √2∏δ|...e^ Homework Equations Its standard deviation is given by: A)ρ2/δ B)δ/ρ C)√δ|/ρ D)ρ/√δ| E)√δ|/2ρ The Attempt at a Solution...
  36. rhody

    Commercial Software that edits PDF Adobe Acrobat File

    I have a need for software that will convert a .PDF Adobe Acrobat Version 8 file to text that can be imported into MS Word. I do not want a scanning imaging solution, for instance MS Word, Document Imaging. Too many scan errors can result, slowing things down, because of scanning errors that...
  37. Y

    Editing PDF Files with 6.0 Standard Edition

    I want to get a program to edit pdf files. I notice there are still the old 6.0 standard edition available very cheap. Any short coming get that as I am too cheap to get the latest or even the 9 version. I am not trying to do video and all the fancy stuff, just want to create document with...
  38. S

    Roll 2 fair dice, find pdf and cdf

    Hi guys. I have a test tomorrow and I am trying to work out the problems on the review sheet, but I can't figure out this one dealing with pdf and cdf. Roll 2 fair dice and call each outcome (i,j) where i,j = 1,2,...6. Define: X= {i+j if i+j ≤ 6 ; abs.value(i-j) otherwise} A) Find...
  39. ArcanaNoir

    Given marginal pdfs of X and Y, find pdf of Z=X-Y

    Homework Statement The probability density function of the random variables X and Y are given by: f_1(x)= \begin{cases} 2 & -\frac{1}{4}\le x\le \frac{1}{4} \\ 0 & \text{elsewhere} \end{cases} and f_2(y) \begin{cases} \frac{1}{2} & 0\le y \le 2 \\ 0 & \text{elsewhere} \end{cases}...
  40. T

    Find PDF of X^3 Given X~N(μ,σ²)

    Let X~N(μ,σ²). Find the PDF of Y=X^3. X is distributed normally with mean mu and variance sigma squared. PDF=probability density function. How would you go about solving this, I am fairly inexperienced with this stuff.
  41. M

    Probablity Question - Joint PDF Expectation/Variance

    Homework Statement I have been given a joint PDF for X and Y, with ranges Y>X≥0. I need to find the E(x) and E(y). Homework Equations I know E(x) = ∫(x)*(f(x,y) dx and E(y) = ∫(y)*(f(x,y)) dyThe Attempt at a Solution For ∫x*f(x,y) dx, i used the limits = x to ∞ For ∫y*f(x,y) dy, i used the...
  42. D

    PDF of breaking a stick

    Homework Statement Consider a stick with unit length. We break at a point, the distance from which to the left end is a random variable X. Find the PDF of Z=|X-y|, where y is a set point between [0,1] (hint: define an event A and write fZ(z) = P(A)fZ|A(z) + P(Ac)fZ|Ac(z)). The Attempt at a...
  43. A

    Integration of a pdf, expected value

    Homework Statement Show that E[Y^4] = 3, where Y~N(0,1) Homework Equations E[(Y-mu)^4]/[E(Y-mu)^2]^2 = 3 E(Y^4) = 1/sprt(2pi)*intregral (y^4)*e^(-y^2/2) The Attempt at a Solution I have expanded and simplified the first equation above and cannot get it to equal 3. I think it's...
  44. D

    Conditional PDF and Expectation: How to Calculate Them?

    The random variable X has the PDF fX(x) = cx^-2 if 1 < x < 2; 0 otherwise: (a) Determine the value c (b) Let A be the event fX > 1.5. Calculate the conditional expectation and the conditional variance of X given A. I'm not understanding the concept of conditional pdf's. Can someone show me the...
  45. L

    Statistics PDF and change of variable

    If the probability density of X is given by f(x) = {2(1 − x) for 0 ≤ x ≤ 1 {0 otherwise (a) Find the probability density function of Y1 = 2X − 1. I do not know how to start this problem can someone please help. Is there a formula that I am missing from my notes to solve this problem?
  46. A

    Find the constant that makes f(x,y) a PDF

    Homework Statement Find the value of k that makes this a probability density function. The question does not specify whether X and Y are independent or dependent. That is actually another part this question. Homework Equations Let X and Y have a joint density function given by f(x,y)...
  47. S

    Conditional PDF with multiple random variables

    Homework Statement D = (L + E) / S Where L, E, and S are mutually independent random variables that are each normally distributed. I need to find (symbolically), the conditional PDF f(d|s). Homework Equations The Attempt at a Solution Not sure what to do with so many...
  48. M

    Calculating moments of forces/fulcrum PDF file attached

    1) see pdf for question 2 I'm unsure how to calculate the force at the fulcrum since its not in equilibrium. I thought maybe i would add the two forces together, but that doesn't seem right. 2) so this question asks for what forces need to be applied at points A and B and i understand...
  49. schrodingerscat11

    Manipulating data in PDF Files with a program

    Homework Statement I am currently doing my thesis, and the gravimetric analysis data I receive from a partner laboratory is in the form of tables in PDF Files. I need to plot the data. It would be tedious if I copy and paste every cell manually, so I decided to automate it using a program...
  50. F

    LaTeX Error in latex and cant open the PDF

    when i want to compile this error appear and it cannot open the PDF could't find input index file: C:\users\farbod\Desktop\1f\1f\PAPER L nor C:\Users\farbod\Desktop\1f\1f\PAPER L.idx.Usage: C:\Program Files (x86)\MiKTeX 2.9\miktex\bin\makeindex.exe [-ilqrcgLT] [-s sty] [-o ind] [-t...
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