Tagged Questions
0
votes
2answers
57 views
Correlations of correlations using 3 data sets
I'm interested in how 14 environmental parameters co-vary with other environmental parameters and whether they show the same patterns in 3 regions. So 1st, I made a pairwise correlation table of the ...
0
votes
1answer
62 views
Correlation of Fixed Effects in lmer
I'm a psycholinguistics student with few knowledge in statistics and I have some doubts about a Correlation of Fixed Effects in lmer function (lme4 package). So, if my question is stupid… hummm… I'm ...
0
votes
0answers
40 views
Comparing two models
I have data for the same response variable but measured in two different areas (Ra and Rb). I want to use the same explanatory data (E) to predict each response in turn:
Ra ~ E
then
Rb ~ E
I then ...
2
votes
2answers
72 views
How to check for a relationship between water bacterial levels
I have a set of data:
http://pastebin.com/KHLKD8XB
which is based on TVC (total viable counts - i.e., numbers of bacteria) from water going into a machine (BM), water taken from the machine (IM) ...
1
vote
1answer
66 views
What is the best way of presenting a correlation? (in R)
I have two variables which show significant correlation (Spearman). I would like to graphically show the strength of the relationship, much like showing a linear regression fit with confidence bands. ...
3
votes
0answers
38 views
Which variables are driving correlations within groups
I'm running an analysis on a few data sets that each typically have 100-200 cases measured across 120-160 variables - something similar to looking at gene expressions. Each variable is a non-centered ...
0
votes
1answer
116 views
Multiple Choice on Linear Regression
1. Which one is NOT a linear regression models? Please give a 1-2 sentences brief
explanation to your choice.
(a) $y_i = β_0 +\exp(β_1x_i)+E_i, i = 1, 2, \ldots, n$
(b) $y_i = β_0 + β_1x_i + β_2 ...
5
votes
2answers
133 views
spatial autocorrelation for time series data
I have a 20-yr dataset of an annual count of species abundance for a set of polygons (~200 irregularly shaped, continuous polygons). I have been using regression analysis to infer trends (change in ...
1
vote
1answer
95 views
vector fit interpretation NMDS
So a colleague and myself are using principal component analysis (PCA) or non metric multidimensional scaling (NMDS) to examine how environmental variables influence patterns in benthic community ...
0
votes
1answer
156 views
Matlab or R: relationship between categorical vs continuous variable
I have a six groups=[1:6] ACTid and a resulting continuous variable observed for each of the members is the group: Y
...
0
votes
0answers
65 views
Robust statistical methods to estimate relationship between variables
I have a dataset with measured co2 fluxes for 5 years and also the corresponding meteorological data (pressure, temperature, humidity etc.) and soil data (soil moisture, temperature). I was able to ...
1
vote
1answer
80 views
How to calculate the HHG (Heller Heller Gorfine) distance in R
In looking at this question and investigating some recent developments in measuring correlation, I came across the HHG (Heller Heller Gorfine) test. Heller et al. promote it as superior to the ...
2
votes
1answer
219 views
Spearman correlation in the presence of many ties - how to spot a problem?
I'm testing the hypothesis that there's a monotonic relationship between two variables. I think I should use a Spearman rank correlation test, since my data don't necessarily meet normality ...
0
votes
0answers
76 views
Differences between visualization of correlation line fit and R^2
I have to figures below, generated using R`s lm function.
If you notice Figure A (above) has higher R^2 value than Figure B (below).
But visually, it is clearly that data in Figure B fits better with ...
0
votes
0answers
46 views
Correlation between task type and measures
I'm pretty new to statistics in general; maybe someone can edit the title to provide a better idea of my question.
The data I'm working with represents refined data extracted from browser log files ...
3
votes
2answers
155 views
Suppose that $R^2=0$ . Does this imply that Y and X are unrelated? [duplicate]
Possible Duplicate:
Under what conditions does correlation imply causation?
Can somebody illustrate how there can be dependence and zero covariance?
Or could there still be a ...
2
votes
1answer
99 views
How to generate two negatively correlated random series of numbers? [duplicate]
Possible Duplicate:
How to generate correlated random numbers (given means, variances and degree of correlation)?
I have been trying to generate two random variables with correlation of ...
1
vote
1answer
328 views
Why does the Phi coefficient approximates the Pearson's correlation?
Going through the Wiki article on the Phi coefficient, I've noticed that for paired binary data "a Pearson correlation coefficient estimated for two binary variables will return the phi coefficient".
...
2
votes
0answers
133 views
Matrix of correlations between the residuals in a SEM fitted by R systemfit function
Assume we would fit this model with systemfit() from the systemfit R package.
$y = \beta_1 x + \gamma_1 z + u$
$z = \beta_2 w + \gamma_2 y + v$
Now I can get an ...
2
votes
1answer
123 views
Correlation with different vector length - same time period
I have a data set containing equity price information on a tick by tick basis.
I would like to calculate the correlation in R, which isn't a hassle.
But the vectors are of different length due to one ...
0
votes
1answer
62 views
How to generate more than two correlated series in R?
I'd like to generate more than two (i.e 3) correlated series, take an example when the series follows an IMA(1,1) process, at first I want to generate three correlated random errors ...
0
votes
0answers
51 views
How to generate 3 correlated random series where all follows MA(1) process in R
I'd like to be sure if the following code is correct.
...
3
votes
2answers
148 views
p-value for correlation/co-occurrence in sets of intervals
I'd like to have a probability measure for the co-occurrence of intervals in two datasets of intervals.
...
1
vote
1answer
182 views
statistical analysis between two time series
I have two time series, which by looking at they appear to be correlated i.e. when one is high the other is high, and when one is low the other is low. Besides looking at the figure and saying these ...
1
vote
0answers
98 views
Correlation analysis
I'm trying to measure the impact that rainfall causes in the number of incoming calls in a insurance-company. I have 4 years of daily data.
The plots below shown the correlation plot for each year:
...
2
votes
0answers
166 views
Compute Moran's I or some other estimate of spatial correlation in R
I'm trying to do a little spatial analysis--just some simple spatial correlations. I have a data frame consisting of latitude and longitudinal points, a value to model, and a neighborhood indicator. ...
0
votes
0answers
62 views
Why does NNLS only pick weakly correlated variables?
I have been looking to find an answer to this problem but haven't had much luck.
My problem has high multicollinearity and hence I am using NNLS (non negative least squares) in R. I am regressing ...
1
vote
0answers
54 views
NNLS in R correlation of variables
I am trying to fit some variables which are high collinear using nnls(non negative least squared routine) in R.
I have about 1 million observations and 200 highly collinear variables for the ...
4
votes
1answer
162 views
Is there a better way to create variables with a certain correlation and one of them is heteroskedastic?
My goal is to generate two variable which are correlated and one of them is heteroscedastic with regards to an grouping variable.
To create two variables with a desired correlation the common way to ...
1
vote
0answers
147 views
Fit lme in R with multiple levels of grouping and with correlation structure defined for more than inner-most level of grouping?
I’m trying to model the correlation/covariance between a pair of variables measured concurrently and repeatedly on a group of subjects. Since both variables are measured responses I want to avoid ...
1
vote
2answers
71 views
Statistical test to find variable causing failure
I have a database with tests that are either a pass or fail and around 25 description fields. Each description field is either a boolean or has between 3 and 10 options.
I'd like to hook into my ...
5
votes
1answer
173 views
Testing for Spatial Autocorrelation in a Negative Binomial Regression Model
Currently, I am working on a count data set measuring events in a third-order administrative unit. The frequency of events varies for each third-order administrative unit to account for the ...
-1
votes
2answers
269 views
Trendline formula in R [closed]
I have created a simple scatterplot to analyse the correlation between two variables, x and y. Using the abline command, I added a trendline to this data. I now want to know the formula for this ...
1
vote
0answers
262 views
Assessing scale reliability: how to get the p-value for corrected item-total correlation?
I assessed the internal reliability of a self-created scale with eight items (N total = 150) by calculating Cronbach’s α. It appears that one item correlates low with the overall score of the scale ...
0
votes
0answers
451 views
Correlation between fitted values and residuals from a linear model in R [closed]
I have a regression model called trees.lm. I calculated residuals as
resid(trees.lm) and ...
1
vote
0answers
89 views
Correlate bivariate Brownian bridges
Given two independently constructed Brownian bridges (from their marginal means and variances), is there a way to correlate the sample paths?
7
votes
3answers
473 views
How to find similarities between time series?
In the following example I have a data frame which consists of a time series of water temperature measurements recorded at 5 depths in the ocean where each value in ...
2
votes
3answers
567 views
Correlation plots with missing values
I have 9 vectors of numeric data. I want to make correlation plots for these 9 vectors. However some vectors are of a different length to others - some have up to 240 observations while others have ...
0
votes
2answers
206 views
How to calculate group statistics in R [duplicate]
Possible Duplicate:
R: compute correlation by group
I have a data set with a 6 or so data points for groups of data.
e.g.:
...
2
votes
0answers
456 views
Generate three correlated uniformly random variables
Suppose we have
$$X_1 \sim \textrm{unif}(n,0,1),$$
$$X_2 \sim \textrm{unif}(n,0,1),$$
where $\textrm{unif}(n,0,1)$ is uniform random sample of size n,
and
$$Y=X_1,$$
$$Z = 0.4 X_1 + \sqrt{1 - ...
0
votes
1answer
259 views
Finding the correlation of every row and column between 2 matrices in R, then taking the max and min values
I'm using R, and I need to find the correlation between every row and column of matrix A and B (ex: the correlation between the 1st row of matrix A and 1st column of matrix B, 2nd row of matrix A and ...
3
votes
2answers
208 views
How to calculate the correlation between smoking patients and heart attacks for each country?
I have a set of data on smoking patients and heart attack on different time points for 25 countries.
How can I calculate the correlation between the smoking patients and heart attacks for each ...
1
vote
1answer
572 views
Permutation tests in R for correlations
What's the easiest way to run permutation tests for a bivariate Pearson correlation matrix in R?
I have tried running MPT.Corr, Multivariate Permutation Test
for Correlations by Urbano Blackford et ...
1
vote
0answers
105 views
Within group correlation of pearson's residuals
I have social network data in which an "ego" names a friend "alter". I am running a regression in R in which attributes of alter are predictors of outcomes for ego. So each observation is dyadic with ...
2
votes
1answer
65 views
Suggestions for computing correlations between evaluators
I have a data frame consisting of evaluations made by students of other student fellows. An excerpt of the evaluations data frame looks like this (columns are evaluators, rows correspond to the ...
1
vote
2answers
609 views
How to determine the number of clusters when using correlation as the distance?
How does using 1 - correlation as the distance influence the determination of the number of clusters when doing kmeans?
Is it still valid to use the classical indices (Dunn, Davies-Bouldin...)?
1
vote
1answer
193 views
how to find a linear combination of predictors maximizing correlation between its score and dependent variable in R
Please correct me if I am wrong as I am not good at R. I think I can find a linear combination maximizing correlation between predictors and dependent variables by running partial least squares ...
2
votes
3answers
4k views
Correlation between matrices in R
I have problems in using the cor() and cor.test() functions.
I just have two matrices (only numerical values, and the same ...
1
vote
2answers
559 views
What type of test to use to determine correlation/relationship between two non-continuous varaibles
I need to determine if there is any relationship between two count variables.
I have 60+ observations for 4 variables and I want to see if any of the pairs of these variables are significantly ...
1
vote
0answers
307 views
When can I use STL decomposition?
Let us say I extract all tweets containing a certain hashtag (main subject of the tweet) and bin them by the hour i.e. count the number of tweets that occurred during a certain hour. I will then be ...
