从R中的加载对象创建json字符串

Question

After performing a factor analysis the loadings object looks like this:

Loadings:
    Factor1 Factor2
IV1  0.844  -0.512 
IV2          0.997 
IV3         -0.235 
IV4         -0.144 
IV5  0.997         

               Factor1 Factor2
SS loadings      1.719   1.333
Proportion Var   0.344   0.267
Cumulative Var   0.344   0.610

I can target the factors themselves using print(fit$loadings[,1:2]) to get the following.

       Factor1      Factor2
IV1 0.84352949 -0.512090197
IV2 0.01805673  0.997351400
IV3 0.05877499 -0.234710743
IV4 0.09088599 -0.144251843
IV5 0.99746785  0.008877643

I would like to create a json string that would look something like the following.

"loadings": {
    "Factor1": {
        "IV1": 0.84352949, "IV2":0.01805673, "IV3":0.05877499, "IV4": 0.09088599, "IV5": 0.99746785
    },
    "Factor2": {
        "IV1": -0.512090197, "IV2": 0.997351400, "IV3": -0.234710743, "IV4": -0.144251843, "IV5": 0.008877643
    }
}

I have tried accessing the individual properties using unclass(), hoping that I could then loop through and put them into a string,have not had any luck ( using loads <- loadings(fit) and <- names(unclass(loads)) names shows up as "null")

Answer 1

Just seconding @GSee's comment (+1) and @dickoa's answer (+1) with a closer example:

1. Creating some demo data for reproducible example (you should also provide one in all your Qs):

    > fit <- princomp(~ ., data = USArrests, scale = FALSE) 

2. Load RJSONIO / rjson packages:

    > library(RJSONIO) 

3. Transform your data to fit your needs:

    > res <- list(loadings = apply(fit$loadings, 2, list)) 

4. Return JSON:

    > cat(toJSON(res)) { "loadings": { "Comp.1": [ { "Murder": -0.041704, "Assault": -0.99522, "UrbanPop": -0.046336, "Rape": -0.075156 } ], "Comp.2": [ { "Murder": 0.044822, "Assault": 0.05876, "UrbanPop": -0.97686, "Rape": -0.20072 } ], "Comp.3": [ { "Murder": 0.079891, "Assault": -0.06757, "UrbanPop": -0.20055, "Rape": 0.97408 } ], "Comp.4": [ { "Murder": 0.99492, "Assault": -0.038938, "UrbanPop": 0.058169, "Rape": -0.072325 } ] } }> 

Answer 2

You can do something along these lines

require(RJSONIO) ## or require(rjson)

pca <- prcomp(~ ., data = USArrests, scale = FALSE)
export <- list(loadings = split(pca$rotation, rownames(pca$rotation)))
cat(toJSON(export))

## {
##     "loadings": {
##         "Assault": [ 0.99522, -0.05876, -0.06757, 0.038938 ],
##         "Murder": [ 0.041704, -0.044822, 0.079891, -0.99492 ],
##         "Rape": [ 0.075156, 0.20072, 0.97408, 0.072325 ],
##         "UrbanPop": [ 0.046336, 0.97686, -0.20055, -0.058169 ] 
##     }
## }

If you want to export it :

cat(toJSON(export), file = "loadings.json")

If it doesn't really suit your need, just modify the data structure ( export object) to the output you want.