Displaying 10 results from an estimated 10 matches for "helsel".
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selsel
2008 Sep 03
2
basic dataframe question
...ng:
Why does my logical vector becomes a numeric vector when stuffed into a data frame? How do I change this so that it's retained as a logical data type? I've tried a couple of things but to no avail.
Here's my example code:
# Exercise 4-1 in Non-Detects and Data Analysis. Dennis Helsel. 2005.
# "Create two new variables in the Interval Endpoints format, StartCu and EndCu,
# that will contain the same information given by the current variables
library(NADA)
data(CuZn)
names(CuZn)
StartCu <- ifelse(CuZn$CuCen == "TRUE", 0, CuZn$Cu)
EndCu <- CuZn$Cu
CuIEP =...
2012 Aug 15
1
NADA package/cenboxplot() method: maximum censored percentage
...et of data has censored (less-than detection limits) water chemistry
concentrations for 80-100% of all observations. My initial trial-and-error
attempts to apply the cenboxplot() method suggests that it has an upper
limit to the percentage of censored observations. I do not see this limit in
Dennis Helsel's second edition.
Has anyone experience plotting censored data and can provide me with the
maximum percentage of censored data in a set of observations?
TIA,
Rich
2024 Jan 24
1
Use of geometric mean for geochemical concentrations [RESOLVED]
...ral Storm Water Discharge Permit for a point
source such as a livestock feed lot you need only a single sample (after the
rains start) to comply with the permit. Feh!
Germane to Bert's comments about all the wrong ways to treat
non-detected/censored water chemical analyses, I discovered Dennis Helsel by
his 2005 article in Environmental Science & Technology (Oct. 16th). Bought
his book when it was published in 2012 and have used survival analyses on
censored data ever since. (Also presented a Continuing Legal Education talk
in 2016 with a nice thank-you email from a state district judge who...
2012 Jun 05
0
NADA Applied to my Data
I need a nudge in the right direction to get started using NADA. I bought
Helsel's second addition and am currently reading it; NADA is installed in
R.
My data has been restructured with a couple of awk scripts. The data frame
structure now has a flag if the quantity is censored (ceneq1 column) as well
as a lower and upper limit for censored data. For present purposes,...
2012 Jun 06
0
R-help Digest, Vol 112, Issue 6
...oject.org
> Subject: [R] NADA Applied to my Data
> Message-ID:
> <alpine.LNX.2.00.1206050931300.27613@salmo.appl-ecosys.com>
> Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII
>
> I need a nudge in the right direction to get started using NADA. I
bought
> Helsel's second addition and am currently reading it; NADA is installed
in
> R.
>
> My data has been restructured with a couple of awk scripts. The data
frame
> structure now has a flag if the quantity is censored (ceneq1 column) as
well
> as a lower and upper limit for censored...
2005 Dec 17
2
diagnostic functions to assess fitted ols() model: Confidence is too narrow?!
Dear all,
When fitting an "ols.model", the confidence interval at 95% doesn't cover
the plotted data points because it is very narrow.
Does this mean that the model is 'overfitted' or is there a specific amount
of serial correlation in the residuals?
Which R functions can be used to evaluate (diagnostics) major model
assumptions (residuals, independence, variance) when
2008 May 12
4
Left censored responses in mixed effects models
Dear R Fellow-Travellers:
What is your recommended way of dealing with a left-censored response
(non-detects) in (linear Gaussian) mixed effects models?
Specifics: Response is a numeric positive measurement (of volume, actually);
but when it falls below some unknown and slightly random value (depending on
how the sample is prepared and measured), it cannot be measured and is
recorded as 0.
2024 Jan 22
3
Use of geometric mean for geochemical concentrations
A statistical question, not specific to R.
I'm asking for a pointer for a source of definitive descriptions of what
types of data are best summarized by the arithmetic, geometric, and harmonic
means.
As an aquatic ecologist I see regulators apply the geometric mean to
geochemical concentrations rather than using the arithmetic mean. I want to
know whether the geometric mean of a set of
2010 Jul 06
3
Help With ANOVA (corrected please ignore last email)
Sorry i had a misprint in the appendix code in the last email
Hi I needed some help with ANOVA
I have a problem with My ANOVA
analysis. I have a dataset with a known ANOVA p-value, however I can
not seem to re-create it in R.
I have created a list (zzzanova) which contains
1)Intensity Values
2)Group Number (6 Different Groups)
3)Sample Number (54 different samples)
this is created by the
2012 Aug 31
3
fitting lognormal censored data
Hi ,
I am trying to get some estimator based on lognormal distribution when we have left,interval, and right censored data. Since, there is now avalible pakage in R can help me in this, I had to write my own code using Newton Raphson method which requires first and second derivative of log likelihood but my problem after runing the code is the estimators were too high. with this email ,I provide