Description Usage Format Details Examples

This example is a character recognition task: classification of handwritten numerals. This problem captured the attention of the machine learning and neural network community for many years, and has remained a benchmark problem in the field.

1 |

The format is: num [1:7291, 1:257] 6 5 4 7 3 6 3 1 0 1 ...

Normalized handwritten digits, automatically scanned from envelopes by the U.S. Postal Service. The original scanned digits are binary and of different sizes and orientations; the images here have been deslanted and size normalized, resulting in 16 x 16 grayscale images (Le Cun et al., 1990).

The data are in two gzipped files, and each line consists of the digit id (0-9) followed by the 256 grayscale values.

There are 7291 training observations and 2007 test observations, distributed as follows: 0 1 2 3 4 5 6 7 8 9 Total Train 1194 1005 731 658 652 556 664 645 542 644 7291 Test 359 264 198 166 200 160 170 147 166 177 2007

or as proportions: 0 1 2 3 4 5 6 7 8 9 Train 0.16 0.14 0.1 0.09 0.09 0.08 0.09 0.09 0.07 0.09 Test 0.18 0.13 0.1 0.08 0.10 0.08 0.08 0.07 0.08 0.09

The test set is notoriously "difficult", and a 2.5 excellent. These data were kindly made available by the neural network group at AT&T research labs (thanks to Yann Le Cunn).

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | ```
findRows <- function(zip, n) {
# Find n (random) rows with zip representing 0,1,2,...,9
res <- vector(length=10, mode="list")
names(res) <- 0:9
ind <- zip[,1]
for (j in 0:9) {
res[[j+1]] <- sample( which(ind==j), n ) }
return(res) }
# Making a plot like that on page 4:
digits <- vector(length=10, mode="list")
names(digits) <- 0:9
rows <- findRows(zip.train, 6)
for (j in 0:9) {
digits[[j+1]] <- do.call("cbind", lapply(as.list(rows[[j+1]]),
function(x) zip2image(zip.train, x)) )
}
im <- do.call("rbind", digits)
image(im, col=gray(256:0/256), zlim=c(0,1), xlab="", ylab="" )
``` |

```
[1] "digit 0 taken"
[1] "digit 0 taken"
[1] "digit 0 taken"
[1] "digit 0 taken"
[1] "digit 0 taken"
[1] "digit 0 taken"
[1] "digit 1 taken"
[1] "digit 1 taken"
[1] "digit 1 taken"
[1] "digit 1 taken"
[1] "digit 1 taken"
[1] "digit 1 taken"
[1] "digit 2 taken"
[1] "digit 2 taken"
[1] "digit 2 taken"
[1] "digit 2 taken"
[1] "digit 2 taken"
[1] "digit 2 taken"
[1] "digit 3 taken"
[1] "digit 3 taken"
[1] "digit 3 taken"
[1] "digit 3 taken"
[1] "digit 3 taken"
[1] "digit 3 taken"
[1] "digit 4 taken"
[1] "digit 4 taken"
[1] "digit 4 taken"
[1] "digit 4 taken"
[1] "digit 4 taken"
[1] "digit 4 taken"
[1] "digit 5 taken"
[1] "digit 5 taken"
[1] "digit 5 taken"
[1] "digit 5 taken"
[1] "digit 5 taken"
[1] "digit 5 taken"
[1] "digit 6 taken"
[1] "digit 6 taken"
[1] "digit 6 taken"
[1] "digit 6 taken"
[1] "digit 6 taken"
[1] "digit 6 taken"
[1] "digit 7 taken"
[1] "digit 7 taken"
[1] "digit 7 taken"
[1] "digit 7 taken"
[1] "digit 7 taken"
[1] "digit 7 taken"
[1] "digit 8 taken"
[1] "digit 8 taken"
[1] "digit 8 taken"
[1] "digit 8 taken"
[1] "digit 8 taken"
[1] "digit 8 taken"
[1] "digit 9 taken"
[1] "digit 9 taken"
[1] "digit 9 taken"
[1] "digit 9 taken"
[1] "digit 9 taken"
[1] "digit 9 taken"
```

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