Gov2001 March 2006

gov2001@lists.gking.harvard.edu

41 participants
66 discussions

[gov2001-l] New Uploads * See Optimization in Practice

by dhopkins＠fas.harvard.edu

Hi All, We've uploaded Problem Set 4, Solution Set 3, today's section handout, and the R code for today's section to the course webpage. Following tonight's sections, for those curious to learn more about how optimization works, the following website lets you experiment with the BFGS algorithm and can be quite instructive: http://www.cse.uiuc.edu/eot/modules/optimization/BFGS/ For a problem with multiple modes, try a function such as: sin(x)+sin(y) Best, Dan ---- Ph.D. Student Department of Government Harvard University Tutor, Currier House dhopkins(a)fas.harvard.edu http://www.danhopkins.org

18 years, 1 month

[gov2001-l] Problem 2b

by tanasa＠fas.harvard.edu

Hello, I was wondering, in problem 2b,c can I safely assume integer values for my gamma function? -- Serban Tanasa Email: tanasa(a)fas.harvard.edu Cell: 617-833-7847 Address: 513 Cabot Mail Center, Cambridge, MA 02138

18 years, 1 month

[gov2001-l] graphing problem 4d

by sheldon.bond＠gmail.com

Greetings, I have not been able to get the perspective graph to work. I have two variables as an output for the multivariate normal distribution. I don't know what the third variable should be. Should I have more outputs for the multivariate normal? Sheldon

18 years, 1 month

[gov2001-l] Re: Interpreting contour plots

by jchattop＠fas.harvard.edu

Hi all, Could someone please explain how to read a contour plot as a means of determining whether there is a relationship between the variables used to construct it? I understand contour plots in topography, but I don't quite see the logic as we're using it here. The only thing I can figure is that a series of concentric rings that are more or less a circle suggest no relationship (i.e. sigma_{1,2}=0), while a contour plot whose rings form more of a football shape or cigar shape indicates a stronger relationship. Is this heading in the right direction? The Cleveland text wasn't of much help. Thanks, Jacqueline -- Jacqueline Chattopadhyay Ph.D Student, Government & Social Policy Harvard University jchattop(a)fas.harvard.edu jchattop(a)gmail.com 714.313.7022

18 years, 1 month

[gov2001-l] LaTeX wrapping equations

by king＠harvard.edu

the amsmath package is very good with all sorts tricks. See my web page under classes. Gary -----Original Message----- From: Ian Brett Yohai <yohai(a)fas.harvard.edu> Date: Wednesday, Mar 8, 2006 9:20 pm Subject: Re: [gov2001-l] LaTeX wrapping equations Hi Stephen, Look at the \lefteqn syntax. You might also look at the amsmath package which has more options for this sort of thing. Best, Ian On Wed, 8 Mar 2006, Stephen Purpura wrote: > How do you convince LaTeX to wrap an equation when it is in a \begin{eqnarray*) construct? > My ln() equations run over a single line. > _______________________________________________ gov2001-l mailing list gov2001-l(a)lists.fas.harvard.edu http://lists.fas.harvard.edu/mailman/listinfo/gov2001-l _______________________________________________ gov2001-l mailing list gov2001-l(a)lists.fas.harvard.edu http://lists.fas.harvard.edu/mailman/listinfo/gov2001-l

18 years, 1 month

[gov2001-l] Question about Covariance Matrix

by sheldon.bond＠gmail.com

When imagining the multivariate normal distribution, the sigma matrix does not seem to be positive definite. This keeps giving me an error when using the mvrnorm function. Is this an error on the homework I missed, or am I in left field somewhere. Sheldon

18 years, 1 month

[gov2001-l] problem 2a

by jfvargas＠fas.harvard.edu

Hi Ian and Dan, A quick question about 2a. Do we have to do all the math involving the derivation of the negative binomial? Or this is just about showing for the case of that distribution that we know what the steps of creating our own distribution are, without actually solving the ugly integral. Juan

18 years, 1 month

[gov2001-l] Question on Problem 3

by ehickey＠fas.harvard.edu

Hi List, I've been working on problem 3, and I have a handle on how to get the Inverse CDF from the lecture notes. However, I'm a little lost on the integration of the Weibull. Should we use the grid method, or go with traditional integration? I was just wondering, since the examples for the grid method we have are for joint densities, and the Weibull doesn't seem to be one (correct me if I'm wrong!) Thanks, Emily

18 years, 1 month

[gov2001-l] Recoding selected values

by jchattop＠fas.harvard.edu

Hey all, Can someone please remind me how to replace all the values within a vector of numbers that meet a certain criterion with another value? For example, if we have a vector [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] and want to repalce all of the values in this vector that are less than or equal to 4 with the number 12, what R code would do this? I've tried to find help in the Fox book and online and appear incapable of locating it. Thanks, Jacqueline -- Jacqueline Chattopadhyay Ph.D Student, Government & Social Policy Harvard University jchattop(a)fas.harvard.edu jchattop(a)gmail.com 714.313.7022

18 years, 1 month

[gov2001-l] Clearing R console

by nall＠fas.harvard.edu

I find that my Xemacs R console is filling up with thousands of lines of garbage (my fault for printing out too much stuff on the screen). I'd like to be able to clear my console of text so I don't have to scroll through it. I remember seeing Ryan Moore do this with couple key strokes last semester. R help doesn't seem to have much.

18 years, 1 month

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Gov2001 March 2006