fitmaanova {maanova} | R Documentation

## Fit ANOVA model for Micro Array experiment

### Description

This is the function to fit the ANOVA model for Micro Array experiment. Given the data and model object, this function will fit the regression gene by gene and output the estimates, variance components for random terms, fitted values, etc. For a mixed effect models, the output estimates will be BLUE and BLUP.

Note that the calculation could be very slow for mixed effect models. The computational time depends on the number of genes, number of arrays and the size of the random variables (dimension of Z matrix).

### Usage

    fitmaanova(madata, mamodel, inits20,
               method=c("REML","ML","MINQE-I","MINQE-UI", "noest"),
               verbose=TRUE)

### Arguments

`madata` | An object of class `madata`.
`mamodel` | An object of class `mamodel`.
`inits20` | The initial value for variance components. This should be a matrix with number of rows equals to the number of genes and number of columns equals to the number of random terms in the model. Good initial values will greatly speed up the calculation. If not given, it will be calculated based on the corresponding fixed model.
`method` | The method used to solve the Mixed Model Equation. Available options includes: "ML" for maximum liklihood; "REML" for restricted maximum liklihood; "MINQE-I" and "MINQE-UI" are for minimum norm and "noest" for no estimate for variance component (use the initial value). Both "ML" and "REML" use method of scoring algorithm to solve MME iteratively. "noest" skips the iteration and will be significantly faster (but accurate). Default method is "REML". For details about fitting mixed effects models, read the "Fitting mixed Effects model" section.
`verbose` | A logical value to indicate whether to display some message for calculation progress.

### Value

An object of class `maanova`, which is a list of following components:

`yhat` | Fitted pmt value which has the same dimension as the input pmt data
`S2` | Variance components for the random terms. It is a matrix with number of rows equals to the number of genes and number of columns equals to the number of random terms. Note that for fixed effect model, S2 is a one column vector for error's variance.
`G` | Gene effects. A vector with the same length as the number of genes.
`reference` | The estimates for reference sample. If there is no reference sample specified in the design, this field will be absent in the output object.
`S2.level` | A list of strings to indicate the order of the S2 field. Note that the last column of S2 is always the error's variance. S2.level is only for the non-error terms. For example, if there are three columns in S2 and S2.level is c("Strain", "Diet"), then the three columns of S2 correspond to the variances of Strain, Diet and error respectively for each gene.
`Others` | Estimates (or BLUE/BLUP for mixed effect model) for the terms in model. There will be XXX.level field for each term representing the order of the estimates (similar to S2.level).
`flag` | A vector to indicate whether there is bad spot for this gene. 0 means no bad spot and 1 means has bad spot. If there is no flag information in input data, this field will not be available.
`model` | The model object used for this fitting.

### Fitting mixed Effects model

Fitting mixed effects models needs a lot of computation. A good starting value for the variances is very important. This function first treats all random factors as fixed and fits a fixed effects model. Then variances for random factors are calculated and used as the initial values for mixed effects model fitting.

There are several methods available for fitting the mixed effects model. "noest" does not really fit the mixed effects model. It takes the initial variance and solve mixed model equatinos to get the estimates (BLUE and BLUP). "MINQE-I" and "MINQE-UI" are based on minimum norm unbiased estimators. It is can be thought as a first iterate solution of "ML" and "REML", respectively. "ML" and "REML" are based on maximum likelihood and restricted maximum likelihood. Both of them need to be solved iteratively so they are verly slow to compute. For "ML" and "REML", a MINQUE estimates is used as the starting value. "Method of scoring" is used as the iteratively algorithm to solve ML and REML. "Method of scoring" algorithm is similar to New-Raphson method except that it uses the expected value of Hessian (second derivative matrix of the objective function) instead of Hessian itself. Method of scoring is more robust to poor starting values and the Hessian is easier to calculate than Newton-Raphson.

For more mathematical details please read Searle et al.

### Author(s)

Hao Wu

### References

Kerr and Churchill(2001), Statistical design and the analysis of gene expression microarrays, Genetical Research, 77:123-128.

Kerr, Martin and Churchill(2000), Analysis of variance for gene expression microarray data, Journal of Computational Biology, 7:819-837.

Searle, Casella and McCulloch, Variance Components, John Wiley and sons, Inc.

### See Also

`makeModel`, `matest`

### Examples

    ###################################
    # fixed model fitting
    ###################################
    # load in Paigen's data
    data(paigen)
    # make data object with rep 2
    paigen <- createData(paigen.raw, 2)
    # Note that the data is normalized so normalization is skipped
    # full model
    model.full.fix <- makeModel(data=paigen,
          formula=~Dye+Array+Spot+Strain+Diet+Strain:Diet)
    anova.full.fix <- fitmaanova(paigen, model.full.fix)
    # residual plot
    resiplot(paigen, anova.full.fix)

    #######################################
    # mixed model fitting -
    # Array, Spot and biological
    # replicates are random effects.
    # This may take a while to finish
    #######################################
    ## Not run:
    model.full.mix <- makeModel(data=paigen,
          formula=~Dye+Array+Spot+Strain+Diet+Strain:Diet+Sample,
          random=~Array+Spot+Sample)
    anova.full.mix <- fitmaanova(paigen, model.full.mix, method="REML")
    # residual plot
    resiplot(paigen, anova.full.mix)
    # variance component plot
    varplot(anova.full.mix)
    ## End(Not run)

[Package maanova version 1.4.0 Index]