Why are some of my created vectors working and others are not for the same method of making sub datasets?

Question

I'm working with a dataset that contains multiple species. To make visualizing the data easier, I have made vectors to divide the data by species.

Here is my data: list of species with sex, weight, and forewing length data - it is part of my datatable

species	sex	weight	forewing length
chlosyne janis	female	0.0555	3.319
chlosyne janis	male	0.0272	3.114
chlosyne janis	male	0.0364	2.756
chlosyne janis	male	0.0278	2.678
chlosyne erodyle	female	0.0593	3.157
chlosyne lacinia crocale	male	0.0364	2.756
chlosyne lacinia crocale	female	0.0143	2.688
chlosyne lacinia crocale	male	0.0085	2.537
chlosyne lacinia crocale	male	0.011	2.25
chlosyne lacinia lacinia	male	0.0164	2.801
chlosyne hippochrome	male	0.0301	1.963
chlosyne acastus neumoegenio	male	0.0121	1.55
anthanassa texana seminole	female	0.0225	1.809
anthanassa texana seminole	female	0.0139	1.491
anthanassa texana seminole	female	0.0179	1.869
anthanassa texana seminole	female	0.0186	1.806
anthanassa texana seminole	female	0.0232	2.125
anthanassa texana seminole	female	0.0143	1.682
anthanassa texana seminole	male	0.017	1.763
anthanassa texana seminole	male	0.0157	1.593
anthanassa texana seminole	male	0.0142	1.393
anthanassa texana seminole	male	0.0152	1.463
anthanassa texana seminole	male	0.0105	1.515
anthanassa texana seminole	male	0.0079	1.485
anthanassa texana seminole	male	0.0185	1.592
anthanassa texana seminole	male	0.0143	1.505
anthanassa texana texana	female	0.0225	1.767
anthanassa texana texana	female	0.0261	1.869
anthanassa texana texana	male	0.0206	1.759

This is a section of the code I've been running:

chlosyne.janis <- tribe.df[tribe.df$species == "chlosyne janis",] 
head(chlosyne.janis) 

chlosyne.erodyle <- tribe.df[tribe.df$species == "chlosyne erodyle",] 
head(chlosyne.erodyle) 

c.lacinia.crocale <- tribe.df[tribe.df$species == "chlosyne lacinia crocale",] 
head(c.lacinia.crocale) 

c.lacinia.lacinia <- tribe.df[tribe.df$species == "chlosyne lacinia lacinia",] 
head(c.lacinia.lacinia) 

chlosyne.hippochrome <- tribe.df[tribe.df$species == "chlosyne hippochrome",] 
head(chlosyne.hippochrome) 

c.acastus.neumoegenio <- tribe.df[tribe.df$species == "chlosyne acastus neumoegenio",] 
head(c.acastus.neumoegenio) 

a.texana.seminole <- tribe.df[tribe.df$species == "anthanassa texana seminole",] 
head(a.texana.seminole) 

a.texana.texana <- tribe.df[tribe.df$species == "anthanassa texana texana",] 
head(a.texana.texana)

For some of the vectors, I can see the number of observations with the associated variables, and for others it will give me 0 observations with the associated variables.

I have double check spelling in the dataset and in the code. c.lacinia.lacinia and c.lacinia.crocale consistently come up with 0 observations, even after reloading the dataset.

Is there a better way to make a vector that retains the observations?

Answer 1

If it is a data.table replace chlosyne.janis <- tribe.df[tribe.df$species == "chlosyne janis",] with chlosyne.janis <- tribe.df[species == "chlosyne janis",]