Questions tagged [vegan]
R package for community and vegetation ecology. Includes ordination methods, diversity analysis, etc.
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13 views
How to determine which species are biggest contributors to overall variation in community?
I have data on the community of microbes from different soil types, however I do not have any environmental variables, only categorical (sites). I have generated PCoAs with distance matrices, however ...
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18 views
Evaluating ecological community over time with NMDS?
I have sampling data of insect communities per month for 7 months. The sampling occurred in the same location with the same methods once a month. I want to be able to see community changes over time ...
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34 views
Comparing species correlations between species in two habitats
I have two community data sets (samples as rows, species as columns, populated with abundance). This data comes from two habitats/sites, with differing numbers of samples at each site.
What I want ...
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5 views
Comparing relative distances between separate ordinations
I have four sites:
Treatment_1 and Control_1 of experiment 1 (8 plots in total)
Treatment_2 & Control_2 of experiment 2 (8 plots in total)
I ran an RDA for each experiment separately to compare ...
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46 views
Repeated Measures Permanova with adonis
I have a between subject variable "treatment" and have a pre and a post measurement for each subject (50 per treatment = 100). The multivariate outcome are bacterial abundances. I control for 2 ...
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0answers
65 views
Variation partition analysis: morphology-climate correlation, controlling for geography
I'm working with three datasets with informations about individuals: morphological data, climatic data of the individual sampling site and geographical data.
My objective is to assess whether ...
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51 views
Remove highly correlated variables before regression - partial or pairwise correlation?
I am using vegan's bioenv() function to find the best (sub)set of variables in one distance matrix (env parameters) that explain the structure of another distance matrix (species abundance).
Several ...
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1answer
88 views
RDA and CCA output- unconstrained inertia 0.00 rank 0
I get an ouput for RDA and for CCA that says that my unconstrained inertia is 0, rank 0. I thought that would be a good thing in the meaning that all the variance in the data is explained by my (...
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20 views
How to choose an ordination method for your dataset?
I'm looking for advice on how to choose the correct/best ordination method for my data.
My data set: Plant species abundance by plot. Approx 150 plots w/ 40 different plant species. The plots are ...
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66 views
metaMDS: Choosing a solution (lower stress vs higher # of dimensions) [closed]
I'm new to ordination and the Vegan package in general. Right now I'm using
the vegan NMDS function (metaMDS) to look at a data set that has species
cover by plot. The data set has a high percentage ...
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0answers
27 views
R, vegan: Is it possible to get effect direction from adonis results?
I used the vegan package and the adonis function to test the impact of a variable on communities.
As far as I understand, the output tells me that there is an effect, but it does not tell me if there ...
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19 views
How to view the predicted unimodal response of a Canonical Correspondence Analysis?
I'm trying to understand the predicted patterns of a Canonical Correspondence Analysis (CCA). I understand one of this method's strengths in understanding ecological patterns lies in its assumption of ...
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61 views
What do standard deviation ellipses mean in an ordination plot?
When kind = 'sd, ordiellipse() draws a single ellipse representing the "standard deviation' around each cluster in an ordination ...
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148 views
Can you use bray-curtis distances to evaluate standardized abundances in an NMDS?
So I'm trying to run an NMDS (using the vegan package in R) for a species X site matrix. Unfortunately the abundances of species are not inherently equal (If you can use that word) meaning that not ...
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248 views
How to code a model with the adonis function in R (permanova) for a paired/matched design (epidemiology study)
We have a database of 100 children that are grouped in 50 paired/matched groups (of 2 children) based on co-variables such as sex, c-section, and antibiotic treatments. We obtained the gut microbial ...
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364 views
R vegan: RDA vs CCA, which test to answer my research question and which results to report?
(if my question should be cut up into sub-questions please let me know, since all those questions are related I decided to ask them here together as one long question)
Main question
As part of my ...
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1answer
314 views
Is Hellinger transformation suitable to access species abundance - environmental variable relationships?
While working with a multivariate dataset, I noticed that Hellinger transformation reveals relationships with the dataset I did not see otherwise. The fact that a transformation affects species ...
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0answers
113 views
Can I use parametric and non-parametric tests in the same publication?
I have a rather difficult dataset. One measurement is non-normal and zero-inflated and could not be transformed to normality. Thus, a glm was used. Another set of ...
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23 views
Model matrix, contrast matrix, transferring tutorial to real data
I have been following this tutorial to perform simple main effects on a multivariate data set that shows a significant interaction between two factors. I can't find any other tutorial that does this ...
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1answer
98 views
Are NMDS Axis the same calculated for one or more dimensions?
I used NMDS axes of an ecological community as proxys for the community similarity in the different samples. I would like to "quantify" the importance of the different NMDS axis according to the ...
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114 views
adonis - data normalisation?
I'm using adonis, an implementation of MANOVA in R (vegan package) to understand how continuous (temperature, pH) and ...
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0answers
45 views
Analysing community composition data at different sites in R
I am trying to analyse some data I have of count data of species collected from samples at two different sites. I am trying to see how community composition varies between the site. It was initially ...
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229 views
Different results using ANOSIM and SIMPER R
I have run ANOSIM and SIMPER to analyse community similarity at two treatments.
When I run ANOSIM the output is:
ANOSIM statistic R: -0.04465
Significance: 0.749
meaning they are similar to ...
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1answer
582 views
Stress values of an nMDS analysis and p-values of ordisurf()
I have run a nMDS analysis in vegan and I have a few questions on the stress values of the analysis as well as the p-values associated with utilizing the ordisurf() function (also in vegan).
First of ...
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84 views
Test for heteroscedasticity of continuous variables in R similar to betadisper()?
Before using adonis() with factors as explanatory variables in R, it is important to check for group dispersion (betadisper()) so that you know whether your significant p-value from adonis is real, i....
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1answer
280 views
Appropriate PERMANOVA (adonis) call for Subject Identity? (Terms drop in output)
I am working with a dataset of microbial species abundances at time points (baseline, 8h, 24h, 48h, 72h, 96h, 120h) for 23 subjects and have weighted unifrac, unweighted unifrac, and Bray-curtis ...
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1answer
298 views
What is the reason behind the name “adonis” (for permutational MANOVA)?
Does any one know why Permutational Multivariate Analysis of Variance Using Distance Matrices (PERMANOVA) is also called adonis?
See
https://www.r-bloggers.com/adonis-permanova-assumptions
or
http://...
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1answer
94 views
How to perform CCA with block design in R
Following example and data are completely fabricated:
Suppose I am studying grooming behaviour in apes. I have four cages, 8 apes in each (4 females + males). For 24 hours I did an observations with ...
2
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1answer
951 views
Betadisper is significant, can I still do ADONIS and ANOSIM?
I'm a grad student in microbial ecology and I'm comparing some bacterial communities in experimental man made ponds. I've run the PCoA, NMDS, and CCA to see how various variables effect or influence ...
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1answer
2k views
adonis in vegan: order of variables — non nested with one degree of freedom for each
I am trying to understand why the order of variables seems to effect p values for both of those variables for the adonis() (Permutational Multivariate Analysis of ...
3
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1answer
291 views
Can MDS coordinates be used as variables in further analyses?
I have calculated an NMDS from vegetation community data taken from two habitat types using the metaMDS() function in vegan. My ...
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1answer
49 views
Should functional groups' abundances be transformed before using RDA?
I want to run Redundancy Analysis (RDA) with the abundance of different functional groups of plants (7 groups in total: shrubs, coniferous, forbs, etc.) as my response variables.
I know that, for ...
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0answers
146 views
Should PERMANOVA be used to select factors for Canonical Correspondence Analysis?
I am interested in investigating the relationship between species composition and several environmental factors. My question is whether it is appropriate to use PERMANOVA to select a 'best' ...
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0answers
133 views
Specification of permutation design in RDA
I am using RDA to study plant communities in various land uses (variable LU with values M, U, etc.). For each land use, I sample 3 to 5 fields (M1, M2, U1, U2, etc). I make 5 measurements for both ...
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1answer
135 views
Calculation of the Shannon Index plotwise or over the entire population
Imagine I inventarized a forest with 28 plots. Do I calculate the Shannon-Index for each plot and take the average, or should I calculate the Shannon-Index over the whole population?
I use R and the ...
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0answers
135 views
Residuals of symmetric Procrustes analyses are not symmetric
I am trying to replicate the analysis I saw in a paper. One of the step is to describe the relationships between two data tables. I use the procrustes() function ...
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56 views
How to apply standardization to train and test dataset in linear regression
Using decostand{Vegan} to standardize a X variable in linear regression:
Approach 1: Should I standardize entire dataset at once?
Approach 2: Should I standardize train and test dataset individually?
...
3
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1answer
141 views
Displaying large number of text labels on a scatter plot
Having too many species in the data, makes the species labels overlap in a plot of a canonical correspondence analysis. This makes it difficult to interpret. Is there a reasonable possible solution?
...
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2answers
79 views
Can I take an average of the values I got from Shannon-Weaver index?
Can I take an average of the values I got from Shannon-Weaver index ? OR Is it wrong to take an average of some values that we get after applying natural logarithm (ln) in an equation, like Shannon-...
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1answer
258 views
Variation partitioning in vegan. Do variables need to be centered?
I would like to carry out variation partitioning to see how landscape variables and local variables contribute to variation in species richness. Do I need to centre my data prior to analysis? ...
2
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1answer
385 views
CCA species coordinates relative to ordination surface
I want to display species coordinates relative to an environmental variable using ordination surface (ordisurf in vegan package)...
4
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1answer
317 views
Standard error for Shannon's index in R
I am interested in examining how the species diversity of bird communities change following timber harvest and have used Vegan in R to run my analyses. Below is a sample of my count data. Plot names ...
