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. P

    What exactly is the difference bet. a CDF and a PDF?

    Homework Statement I understand that PDF is a derivative of CDF and hence CDF is the integral of PDF. But I don't understand the difference between PDF and simply probability? What exactly is the differece? What extra things does PDF tell us which simple probability does not? Homework...
  2. C

    Distribution of a random variable , pdf vs probability distribution

    Hey all i struggling to understand, these concepts. would some explain to me the relationship and differences the distribution of a random variable and a probabiltiy distribution. wikipedia says this about probability distribution "The probability distribution describes the range of possible...
  3. N

    PDF (probability density function)

    Hi everyone, I have a simple question (assuming since it was only worth 5% of total marks in the exam) about the PDF of a random variable. Given that PDF of random signal equals p(X) = \Lambda(X), where \Lambda is the triangle function, what would be the PDF of the random signal Y, Y = -3X...
  4. R

    What is the pdf of resistor values (tolerances)

    Hi guys, I was reading about monte carlo analysis in the introduction from a textbook, and they gave an example of a voltage divider. They assumed resistor values had an equal probability of having values between the two tolerances. I know this is a simplistic assumption and I was wondering...
  5. G

    Determination of a Join pdf

    Determination of a Joint pdf Hi all! Someone can help me with this problem? The duration of a certain type of bulbs has a exponential distribution with known parameter \lambda . Consider a set of n bulbs. Which is the joint pdf of the durations t_{i} of the n bulbs?
  6. R

    Solving Problems 4 & 7 from EM4WS5 PDF

    Homework Statement problems 4 and 7 from this pdf http://www.daisleyphysics.com/y2p/worksheets/em4ws5.pdf Homework Equations The Attempt at a Solution A friend of mine is bad with computers and she asked me to help find the answers.
  7. C

    Finding probability given joint pdf.

    Homework Statement Let X1 X2 X3 be independent and identically distributed random variables with common pdf f(x) = e^-x 0<x<infinity, zero elsewhere. Evaluate P(X1 < X2|X1 < 2X2) and P(X1 < X2 < X3|X3 < 1). The Attempt at a Solution Would appreciate any hints as to where to start...
  8. C

    Finding cdf and pdf of variable.

    Homework Statement Let X1 X2 X3 and X4 be four independent random variables, each with pdf f(x) = 3(1-x)2, 0<x<1, zero elsewhere. If Y is the minimum of these four variables, find the cdf and pdf of Y. The Attempt at a Solution P(Y<or= y) = 1 - P(Y>y) = 1 - P(X1>y, X2>y, X3>y...
  9. C

    Finding joint pdf of independent variables.

    Homework Statement Suppose X1 and X2 are two independent gamma random variables, and X1~Gamma(a1, 1) and X2~(a2, 1). a) Find the joint pdf of Y1 = X1 + X2, and Y2 = X1/(X1 + X2). b) Show that Y1 and Y2 are independent. c) Find the marginal distributions of Y1 and Y2. The Attempt...
  10. I

    How do I effectively normalise the Schrodinger PDF with given conditions?

    Homework Statement Normalise \Psi(x,t) = Ae^{-\lambda |x|}e^{-i \omega t} Homework Equations (i.e. it must satisfy \int_{-\infty}^{\infty} |\Psi (x,t)|^2 dx=1) The Attempt at a Solution This is my first attempt at normalisation and I don't know how valid my reasoning is, can...
  11. R

    Can the pdf be determined numerically for a given data set?

    I have just been learning probability density function (pdf) and there is something I need to ask. I understand the idea that for any value v, the pdf (f(v)) gives the probability that a value picked from a data set is less than v. It seems ok to find mean,variance, skewness etc. when f(v) is...
  12. K

    Uniform/Exponential PDF

    Homework Statement Let X be uniformly distributed over [0, 1] and Y be exponentially distributed with λ=1. Assuming X and Y are independent, give the PDF of Z=X/Y. Homework Equations The Attempt at a Solution I know the individual PDFs of X and Y. I was trying to use a geometric...
  13. A

    Question involving pdf of change of variable

    A Geiger counter records the times at which radioactive particles are detected. However, if two particles occur within a short time θ of each other, the second one is not detected. Then, the probability density function of X, the time between successive recorded detections, is f(x) = k...
  14. S

    How to Convert Between CDF and PDF Functions in Mathematical Equations?

    cdf to pdf and vise versa hi i'm looking for help when going from a cdf function: F(x) = { 1- e^-αx^β x ≥ 0, α>0, β>0 { 0 x < 0 to getting the corresponding pdf also i am looking to do the opposite(pdf to cdf) for: f(x) = { (1 + α)/2 for -1 ≤ x ≤ 1, -1 ≤ α ≤ 1 { 0 otherwise i'm...
  15. S

    How do I convert between cdf and pdf?

    hi i'm looking for help when going from a cdf function: F(x) = { 1- e^-αx^β x ≥ 0, α>0, β>0 { 0 x < 0 to getting the corresponding pdf also i am looking to do the opposite(pdf to cdf) for: f(x) = { (1 + α)/2 for -1 ≤ x ≤ 1, -1 ≤ α ≤ 1...
  16. K

    Joint PDF of a spatial distribution

    Homework Statement In a square town that is 1.5 miles by 1.5 miles, the places of residence are uniformly distributed (2000 per square mile) over the whole town. Compute the joint probability density function for the spatial distribution of places of residence (fX, Y). Homework Equations...
  17. R

    Understanding the CDF & PDF of X's Difference

    Hi guys! Homework Statement Do you know how to get the cdf and pdf of the absolute difference of two iid standard uniform X1 and X2 : X = |X1 − X2| ? Homework Equations Come across...
  18. E

    PDF of Order Statistics for RVs: \gamma_1,\,\ldots,\,\gamma_M

    Hello, Suppose that we have the following set of independent and identically distributed RVs: \gamma_1,\,\gamma_2,\,\ldots,\,\gamma_M. Arranging them in descending order as: \gamma_{1:M}\ge\gamma_{2:M}\ge\cdots\ge\gamma_{M:M}. Now suppose we select the largest m\leq M order statistics. What...
  19. Saladsamurai

    PC Users What do you use to create FREE PDF files?

    How can I create a PDF file w/out buying anything? Why does adobe try to swindle you into buying something? It's cake on my Mac, but on my PC not so much. So what do you guys use? Thanks, Casey
  20. E

    Is there any free way to split PDF pages down the middle?

    Is there any free way to split PDF pages down the middle? I have a scanned PDF book with 2 pages on each page. Is there any way I could split the whole doc down the middle so there is 1 book page per page.
  21. B

    Calculating Randomly Truncated PDF for X given T1 < X < T2

    Hi, all, I am having a problem in calculating a randomly truncated pdf. Let x be a random variable, it's pdf f(x) is known. Let t1 and t2 be anther two random variables, their pdf f(t1) and f(t2) are known as well. Now, how do I compute the pdf f(x|t1<x<t2)? Thks a lot.
  22. N

    Saving part of a PDF file only

    I have a pdf file and I need to save to disk only part of it, not the whole document. Does anyone know how to do that? I have the LaTeX file and I can of course LaTeX only part of the file but the problem is that the references in the part that I LaTeX are then not working since they refer...
  23. B

    Can You Generate Samples from f(x2) Based on f(x1)?

    Hi,all, I have a problem of computing pdf of some random variables. Assuming x1, x2... xN are some random variables. Now, I know the pdf of x1, which is f(x1). For the pdf of x2, it is given as a function of x1, in this case, how do I compute pdf of x2? Or, rather, how do I generate samples...
  24. E

    Finding PDF of Z: X_1, X_2 Exponential RVs

    Hello, Suppose that: Z=X_1+X_2+X_1X_2 where X_i for i=1 and 2 are independent and identically distribuited exponential RVs. can we find the PDF of Z? Regards
  25. H

    Pdf of exponetial distribution

    I am confused as hell. If you look at exponential distribution at wikipedia or elsewhere, you can see that the pdf can attain values larger than 1. How is it possible? This basically implies that probability density of some value is larger than 1? :mad:
  26. E

    Order Statistics PDF and CDF

    Hello, Is the relation between the PDF and CDF of order statistics is as any PDF and CDF. i.e.: F_X(x)=\int_{-\infty}^{x}f_X(t)\,dt Regards
  27. E

    PDF and CDF Integration Simplification

    Hello, I have this equation: \int_{-\infty}^{\gamma}f_X(x)\,dx+\int_{\gamma}^{\infty}F_Y(x-\gamma)\,f_X(x)\,dx where f_X(x) and F_Y(y) are the PDF and CDF of the randome variables X and Y, respectively. Now the question is: can I write the above equation in the form...
  28. B

    Determine pdf of function with gamma pdf

    Homework Statement Hi Guys, I have been given the following The random variable X has a gamma (\alpha,\beta) distribution; ie X has pdf f_{X}(x)=\frac{x^{\alpha-1}e^{\frac{-x }{\beta}}} {\Gamma (\alpha)\beta^{\alpha}}\text{for }x \geq 0 (a) Determine the pdf of...
  29. B

    Expected value of bivariate pdf

    Is the expected value E[x]or E[y] of a bivariate pdf fXY(xy) \int x f(x,y)dx or E[y] \int y f(x,y)dy ? example if f(x,y) = x+y E[X] = \int x *(x+y)dx regards Brendan
  30. G

    Caroll´s GR text: differences between PDF and printed book?

    Dear all, what are the differences between Caroll´s GR published book and the PDF text? Thanks, Goldbeetle
  31. C

    Difference between a PDF and a CDF?

    I'm having a lot of trouble figuring out the difference between a probability density function and a cumulative distribution function. Is the CDF just the integral of the PDF? Thanks in advance.
  32. H

    Finding Marginal Pdf's for a Joint PDF

    Joint PDF --> Marginal Pdf's Homework Statement Suppose that the random vector (X, Y ) has the probability density function (pdf) fX,Y (x, y) = k(x − y), if 0 < y < x < 1 0, otherwise. 1. Find the value of k, so that fX,Y (x, y) is a genuine pdf. 2. Find the marginal...
  33. P

    LaTeX Troubleshooting LaTeX: Cannot Open PDF or View Changes - Expert Tips

    I'm not sure where to have put this question I hope it is in the right place. I have big problem with LaTeX.. I have been writing a document for a while and recently when I click the build and view button it shows this error [DocOpen(%bm.pdf")][FileOPen(%bm.pdf)] Cannot execute the...
  34. P

    LaTeX Problem with LaTeX generating pdf?

    I'm not sure where to have put this question I hope it is in the right place. I have big problem with LaTeX.. I have been writing a document for a while and recently when I click the build and view button it shows this error [DocOpen(%bm.pdf")][FileOPen(%bm.pdf)] Cannot execute the...
  35. P

    PDF of function of 3 continuous, uniform random variables?

    Hi. The question is: Given X, Y and Z are all continuous, independant random variables uniformly distributed on (0,1), prove that (XY)^Z is also uniformly distributed on (0,1). I worked out the pdf of XY=W. I think it's -ln(w). I have no idea at all how to show that W^Z is U(0,1). What...
  36. B

    Determining the PDF Given a DF

    I have been asked to determine the pdf given a DF. F(x) = 0 for x<0 F(x) = x^2/x for x 0<= x < 1 F(X) = x/2 for 1<=x<2 F(x) = 1 for x>= 2 Is the pdf the derivative of the df So if you wanted the probability of x between 0 and 1 The pdf would just be x ? regards Brendan
  37. N

    Nsert this equation in a pdf file

    Homework Statement Hi. I need to insert this equation in a pdf file such that it doesn't cut off. How can I make it appear without cutting off? Homework Equations \noindent\(\sqrt{\frac{1}{2} e^{\frac{1}{2} \text{$\kappa $u} (-4 u+4 \text{u0}+\text{$\kappa $u})} \sqrt{\pi }...
  38. R

    Finding unknown coefficients of a quadratic equation describing a PDF

    Homework Statement I have a probability distribution function (PDF) going fromi 0 to a on the y-axis and 0 to 30 on the x-axis. The function describing the PDF is the quadratic equation f(x) = a+bx+cx^2 I have to find a, b, and c. Homework Equations The Attempt at a Solution...
  39. S

    Finding PDF of Y if X is a Gaussian PDF

    A question which I amnot able to do...please help: Find the PDF of Y if X is a Gaussian PDF: fx(x) = (1e-x^2/2)/(2pi)^1/2 ; -infnity<x<+infinity Express your answer in terms of CDF of X gven by Fi(x) = Integral -infnty to + infnity((1e-x^2/2)/(2pi)^1/2) b) Sketch both the PDF, fY(y)...
  40. W

    PDF App for Linux: Ubuntu-8.10

    I am looking for an application to not only view pdf's but also type side notes and highlight sections. This application must be compatible with my platform: Linux - Ubuntu-8.10. Thanks
  41. N

    What is the PDF of a Sine Wave Cycle?

    Does anybody know what the pdf of a sine wave cycle is? Or perhaps how to derive it? The problem can be done numerically, but surely there is an analytic expression for this function? There is a numerical solution available at...
  42. marcus

    Proofs from Oriti's QG book available in PDF

    Cambridge press says available as of around 1 March, so in a couple of months. Samples are available of page proofs as they will, I gather, appear in the book. Here's the 3-page table of contents http://assets.cambridge.org/97805218/60451/toc/9780521860451_toc.pdf Here's an 11-page exerpt...
  43. X

    Given the pdf of two variable, find the distribution of the function

    Hi all, I am new here. I have a problem about statistics: now I have two variable a & b, both of them are uniformly distributed in [-1 1], I want to find the pdf of the function f=|a-b|/|a+b|. Any hint is welcome, thanks a lot xiaoli
  44. N

    Troubleshooting Bibliography Issues in PDF Output

    Hey all, My bibliography is not showing up in the PDF output, and I'm not sure why.. The bib file is in the same directory as the the main tex file. I am using the command: \documentclass[a4paper,twoside,11pt]{book} \usepackage{calc} \usepackage{setspace} \usepackage{graphicx}...
  45. N

    Free PDF Editor for Windows XP - Add, Remove, Reorder, Resize Pages

    I'm trying to find some software (preferably free) which allows editing of pdf files in Windows XP. I don't need anything too fancy, just the ability to add/remove/reorder/resize pages, and to add and remove bookmarks. Anyone have any suggestions?
  46. A

    Finding Constants for a Gaussian PDF

    Homework Statement The exam grades in a certain class have a Gaussian PDF with mean m and standard deviation \sigma. Find the constants a and b so that the random variable y=aX+b has a Gaussian PDF with mead m' and standard deviation \sigma'. Homework Equations The Attempt at a...
  47. A

    Gaussian PDF: Probability of P(x), Usable Shafts %

    Que. 1 Consider a Gaussian PDF with µ = 20, σ = 30, a = 50 and b =80. Determine i)Probability that P(x>b) ii)P(x ≤ b) iii)P(x ≤ - b) iv)P(a ≤ x ≤ b) Que. 2 In a certain manufacturing process only shafts whose diameters are less than 1.5 inches can be used. Given the shaft diameters are...
  48. M

    Stats - Continious random distribution (PDF)

    Homework Statement A function f( x ) had the following form : f ( x) = kx^-(k+1) where 1 < x < infinity a) for what values of k is f a pdf ? Homework Equations See attachments (the theorem is included) The Attempt at a Solution started out by using the first equation in the...
  49. A

    Mode of a PDF - all data are unique

    Question is what is the mode when all data are unique? have a set wherein the actual question is what is the inference about the PDF for the data? Median > mean but no mode...i was under the impression that PDF is only for a continuous measurements...when data set is unique...in which case it...
  50. A

    Calculating f(x) PDF Mean,Median,Mode & Plotting

    Determine constants A and B such that function f(x) is a valid PDF whose mean is 0.9 times its mode. f(x) = Ax- Bx ^3 , 0 <= x <= 2, otherwise = 0 Also calculate its mean,median and mode and plot the PDF Please help...am scratching my head...have the answers but cannot derive the...
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