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From Shirish Tatikonda <shirish.tatiko...@gmail.com>
Subject Re: DML example on main SystemML website
Date Thu, 17 Dec 2015 06:03:36 GMT
```Deron,

Along with such a complete algorithm, we could also include one/two common
and useful DML snippets. We could also create a "DML Cookbook" with such
snippets and keep adding more over time.
Some example snippets are below -- note that I created them quite a while
back, and they may need revision and testing.

*Classifier Performance*

# Confusion matrix
cm = table(truthLabels, predictedLabels)
TP = as.scalar(cm[1,1])
TN = as.scalar(cm[2,2])
FP = as.scalar(cm[1,2])
FN = as.scalar(cm[2,1])

accuracy = (TP+TN)/nrow(truthLabels)
precision = TP / (TP+FP)
recall = TP / (TP+FN)

print("Accuracy = " + accuracy + ", Precision = " + precision + ", Recall =
" + recall);

*Covariance matrix*

N = nrow(A);
# column means
mu = colSums(A)/N;
# Covarianace matrix
C = (t(A) %*% A)/(N-1) - (N/(N-1))*t(mu) %*% mu;

*Select rows satisfying a predicate*

ind = diag(ppred(A[,1], thresh, ">"));
ind = removeEmpty(target=ind, margin="rows");
result = ind %*% A;

*Center and Scale columns*

cm = colMeans(A);
cvars = (colSums (A^2));
cvars = (cvars - N*(cm^2))/(N-1);
Ascaled = (A-cm)/sqrt(cvars);

*Random shuffling of rows*

N = nrow(A);
s = sample(N, N, replace=FALSE);
tab = table(seq(1:N), s);
result = tab %*% A;

On Wed, Dec 16, 2015 at 5:59 PM, Deron Eriksson <deroneriksson@gmail.com>
wrote:

> That example is perfect. Concise and powerful. Thank you Fred.
>
> Deron
>
>
> On Wed, Dec 16, 2015 at 4:16 PM, Frederick R Reiss <frreiss@us.ibm.com>
> wrote:
>
> > We can use the Poisson nonnegative matrix factorization example from last
> > week's webcast:
> >
> >    i = 0
> >    while(i < max_iterations) {
> >        H = (H * (t(W) %*% (V/(W%*%H + epsilon)))) / t(colSums(W))
> >        W = (W * ((V/(W%*%H) + epsilon) %*% t(H))) / t(rowSums(H))
> >        i = i + 1;
> >    }
> >
> >
> > Sound ok to everyone?
> >
> > Fred
> >
> >
> > [image: Inactive hide details for Deron Eriksson ---12/16/2015 04:02:26
> > PM---Hi, I think the main SystemML website at http://systemml.i]Deron
> > Eriksson ---12/16/2015 04:02:26 PM---Hi, I think the main SystemML
> website
> > at http://systemml.incubator.apache.org/
> >
> > From: Deron Eriksson <deroneriksson@gmail.com>
> > To: dev@systemml.incubator.apache.org
> > Date: 12/16/2015 04:02 PM
> > Subject: DML example on main SystemML website
> > ------------------------------
> >
> >
> >
> > Hi,
> >
> > I think the main SystemML website at
> http://systemml.incubator.apache.org/
> > needs to be updated so that the DML example is an actual algorithm or at
> > least a fragment of an algorithm.
> >
> > Does anyone have a recommendation for a short, concise example that shows
> > the power of DML?
> >
> > Thanks!
> > Deron
> >
> >
> >
>

```
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