Toxicity of Carboxylic Acids Data

The aim of the experiment was to predict the toxicity of carboxylic acids on the basis of several molecular descriptors.

data(toxicity, package="robustbase")

Format

A data frame with 38 observations on the following 10 variables which are attributes for carboxylic acids:

toxicity

aquatic toxicity, defined as \(\log(IGC_{50}^{-1})\); typically the “response”.

logKow

\(log Kow\), the partition coefficient

pKa

pKa: the dissociation constant

ELUMO

Energy of the lowest unoccupied molecular orbital

Ecarb

Electrotopological state of the carboxylic group

Emet

Electrotopological state of the methyl group

RM

Molar refractivity

IR

Refraction index

Ts

Surface tension

P

Polarizability

Source

The website accompanying the MMY-book: https://www.wiley.com/legacy/wileychi/robust_statistics/

References

Maguna, F.P., Núñez, M.B., Okulik, N.B. and Castro, E.A. (2003) Improved QSAR analysis of the toxicity of aliphatic carboxylic acids; Russian Journal of General Chemistry 73, 1792–1798.

Examples

data(toxicity)
summary(toxicity)
#>     toxicity           logKow             pKa              ELUMO      
#>  Min.   :-0.9400   Min.   :-0.5900   Min.   :-0.2000   Min.   :1.860  
#>  1st Qu.:-0.4675   1st Qu.: 0.7375   1st Qu.: 0.2472   1st Qu.:4.393  
#>  Median :-0.2250   Median : 1.5750   Median : 0.8913   Median :4.700  
#>  Mean   :-0.1558   Mean   : 1.6668   Mean   : 0.6489   Mean   :4.344  
#>  3rd Qu.: 0.0800   3rd Qu.: 2.6475   3rd Qu.: 0.9675   3rd Qu.:4.830  
#>  Max.   : 0.9000   Max.   : 4.4200   Max.   : 1.0200   Max.   :4.970  
#>      Ecarb            Emet               RM              IR       
#>  Min.   :15.40   Min.   :-0.8056   Min.   :15.33   Min.   :1.397  
#>  1st Qu.:16.89   1st Qu.: 0.8425   1st Qu.:26.56   1st Qu.:1.425  
#>  Median :17.23   Median : 2.5304   Median :31.43   Median :1.444  
#>  Mean   :17.19   Mean   : 3.1191   Mean   :34.27   Mean   :1.446  
#>  3rd Qu.:17.71   3rd Qu.: 4.5039   3rd Qu.:40.72   3rd Qu.:1.470  
#>  Max.   :18.48   Max.   :11.2898   Max.   :70.03   Max.   :1.478  
#>        Ts              P         
#>  Min.   :30.20   Min.   : 1.422  
#>  1st Qu.:32.55   1st Qu.: 1.462  
#>  Median :33.15   Median : 1.476  
#>  Mean   :38.14   Mean   : 6.808  
#>  3rd Qu.:41.50   3rd Qu.:12.430  
#>  Max.   :70.50   Max.   :21.630  
plot(toxicity)

plot(toxicity ~ pKa, data = toxicity)


## robustly scale the data (to scale 1) using Qn
(scQ.tox <- sapply(toxicity, Qn))
#>    toxicity      logKow         pKa       ELUMO       Ecarb        Emet 
#>  0.40414939  1.45493782  0.12649876  0.24248964  0.70645314  2.62191920 
#>          RM          IR          Ts           P 
#> 12.40738642  0.02424896  2.62697107  0.06668465 
scTox <- scale(toxicity, center = FALSE, scale = scQ.tox)
csT <- covOGK(scTox, n.iter = 2,
              sigmamu = s_Qn, weight.fn = hard.rejection)
as.dist(round(cov2cor(csT$cov), 2))
#>        1     2     3     4     5     6     7     8     9
#> 2   0.91                                                
#> 3  -0.32 -0.17                                          
#> 4  -0.25 -0.05  0.64                                    
#> 5  -0.01  0.28  0.48  0.48                              
#> 6   0.88  0.72 -0.50 -0.54 -0.08                        
#> 7   0.78  0.78 -0.11 -0.06  0.36  0.77                  
#> 8   0.32  0.13 -0.57 -0.84 -0.22  0.70  0.41            
#> 9  -0.28 -0.35 -0.11 -0.50  0.00  0.11  0.14  0.72      
#> 10  0.36  0.18 -0.25 -0.07 -0.06  0.41  0.43  0.24  0.09