Related
I have JSON of the form:
{"abc":
{
"123":[45600],
"378":[78689],
"343":[23456]
}
}
I need to convert above format JSON to CSV file in R.
CSV format :
ds y
123 45600
378 78689
343 23456
I'm using R library rjson to do so. I'm doing something like this:
jsonFile <- fromJSON(file=fileName)
json_data_frame <- as.data.frame(jsonFile)
but it's not doing the way I need it.
You can use jsonlite::fromJSON to read the data into a list, though you'll need to pull it apart to assemble it into a data.frame:
abc <- jsonlite::fromJSON('{"abc":
{
"123":[45600],
"378":[78689],
"343":[23456]
}
}')
abc <- data.frame(ds = names(abc[[1]]),
y = unlist(abc[[1]]), stringsAsFactors = FALSE)
abc
#> ds y
#> 123 123 45600
#> 378 378 78689
#> 343 343 23456
I believe you got the json file reader - fromJSON function right.
df <- data.frame( do.call(rbind, rjson::fromJSON( '{"a":true, "b":false, "c":null}' )) )
The code below gets me Google's Location History (json) archive from https://takeout.google.com. This is if you have enabled a 'Timeline' (location tracking) in Google Maps on your cell. Credit to http://rpubs.com/jsmanij/131030 for the original code. Note that json files like this can be quite large and plyr::llply is so much more efficient than lapply in parsing a list. Data.table gives me the more efficient 'rbindlist' to take the list to a data.table. Google logs between 350 to 800 GPS calls each day for me! A multi-year location history is converted to quite a sizeable list by 'fromJSON':
format(object.size(doc1),units="MB")
[1] "962.5 Mb"
I found 'do.call(rbind..)' un-optimized. The timestamp, lat, and long needed some work to be useful to Google Earth Pro, but I am getting carried away. At the end, I use 'write.csv' to take a data.table to CSV. That is all the original OP wanted here.
ts lat long latitude longitude
1: 1416680531900 487716717 -1224893214 48.77167 -122.4893
2: 1416680591911 487716757 -1224892938 48.77168 -122.4893
3: 1416680668812 487716933 -1224893231 48.77169 -122.4893
4: 1416680728947 487716468 -1224893275 48.77165 -122.4893
5: 1416680791884 487716554 -1224893232 48.77166 -122.4893
library(data.table)
library(rjson)
library(plyr)
doc1 <- fromJSON(file="LocationHistory.json", method="C")
object.size(doc1)
timestamp <- function(x) {as.list(x$timestampMs)}
timestamps <- as.list(plyr::llply(doc1$locations,timestamp))
timestamps <- rbindlist(timestamps)
latitude <- function(x) {as.list(x$latitudeE7)}
latitudes <- as.list(plyr::llply(doc1$locations,latitude))
latitudes <- rbindlist(latitudes)
longitude <- function(x) {as.list(x$longitudeE7)}
longitudes <- as.list(plyr::llply(doc1$locations,longitude))
longitudes <- rbindlist(longitudes)
datageoms <- setnames(cbind(timestamps,latitudes,longitudes),c("ts","lat","long")) [order(ts)]
write.csv(datageoms,"datageoms.csv",row.names=FALSE)
What are the options for visualising the results of a benchmark experiment of regression learners? For instance, generateCalibrationData doesn't accept a benchmark result object derived from a set of regr. learners. I would like something similar to the calibration plots available for classification.
In response to #LarsKotthoff's comment, I (the OP) have edited my original post to provide greater detail as to what functionality I am seeking.
Edit:
I'm looking for actual vs predicted calibration type plots such as simple scatterplots or something like the plots that exist under Classifier Calibration. If I'm not mistaken, the following would make sense for regression problems (and seems to be what is done for Classifier Calibration):
decide on a number of buckets to discretize the predictions on the x-axis, say 10 equal length bins (obviously you could continue with the breaks and groups interface to generateCalibrationData that currently exists)
for each of those bins 10, calculate the mean "predicted" and plot (say via a dot) on the x-axis (possibly with some measure of variability) and join the dots across the 10 bins
for each of those bins 10, calculate the mean "actual" and plot on the y-axis (possibly with some measure of variability) and join the dots
provide some representation of volume in each bucket (as you've done for Classifier Calibration via "rag/rug" plots)
The basic premise behind my question is what kind of visualisation can be provided to help interpret an rsq, mae etc performance measure. There are many configurations of actual vs predicted that can lead to the same rsq, mae etc.
Once some plot exists, switching aggregation on/off would allow individual resampling results to be examined.
I would hope that the combination:
cal <- generateCalibrationData(bmr)
plotCalibration(cal)
would be available for regression tasks, at present it doesn't seem to be (reproducible example below):
# Practice Data
library("mlr")
library(mlbench)
data(BostonHousing)
dim(BostonHousing)
head(BostonHousing)
# Define Nested Cross-Validation Strategy
cv.inner <- makeResampleDesc("CV", iters = 2)
cv.outer <- makeResampleDesc("CV", iters = 6)
# Define Performance Measures
perf.measures <- list(rsq, mae)
# Create Task
bh.task <- makeRegrTask(id = "bh",
data = BostonHousing,
target = "medv")
# Create Tuned KSVM Learner
ksvm <- makeLearner("regr.ksvm")
ksvm.ps <- makeParamSet(makeDiscreteParam("C", values = 2^(-2:2)),
makeDiscreteParam("sigma", values = 2^(-2:2)))
ksvm.ctrl <- makeTuneControlGrid()
ksvm.lrn = makeTuneWrapper(ksvm,
resampling = cv.inner,
measures = perf.measures,
par.set = ksvm.ps,
control = ksvm.ctrl,
show.info = FALSE)
# Create Tuned Random Forest Learner
rf <- makeLearner("regr.randomForest",
fix.factors.prediction = TRUE)
rf.ps <- makeParamSet(makeDiscreteParam("mtry", values = c(2, 3, 5)))
rf.ctrl <- makeTuneControlGrid()
rf.lrn = makeTuneWrapper(rf,
resampling = cv.inner,
measures = perf.measures,
par.set = rf.ps,
control = rf.ctrl,
show.info = FALSE)
# Run Cross-Validation Experiments
bh.lrns = list(ksvm.lrn, rf.lrn)
bh.bmr <- benchmark(learners = bh.lrns,
tasks = bh.task,
resampling = cv.outer,
measures = perf.measures,
show.info = FALSE)
# Calibration Charts
bh.cal <- generateCalibrationData(bh.bmr)
plotCalibration(bh.cal)
which yields:
> bh.cal <- generateCalibrationData(bh.bmr)
Error in checkPrediction(x, task.type = "classif", predict.type = "prob") :
Prediction must be one of 'classif', but is: 'regr'
> sessionInfo()
R version 3.2.3 (2015-12-10)
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] mlbench_2.1-1 ROCR_1.0-7 gplots_3.0.1 mlr_2.9
[5] stringi_1.1.1 ParamHelpers_1.10 ggplot2_2.1.0 BBmisc_1.10
loaded via a namespace (and not attached):
[1] digest_0.6.9 htmltools_0.3.5 R6_2.2.0 splines_3.2.3
[5] scales_0.4.0 assertthat_0.1 grid_3.2.3 stringr_1.0.0
[9] bitops_1.0-6 checkmate_1.8.2 gdata_2.17.0 survival_2.38-3
[13] munsell_0.4.3 tibble_1.2 randomForest_4.6-12 httpuv_1.3.3
[17] parallelMap_1.3 mime_0.5 DBI_0.5-1 labeling_0.3
[21] chron_2.3-47 shiny_1.0.0 KernSmooth_2.23-15 plyr_1.8.4
[25] data.table_1.9.6 magrittr_1.5 reshape2_1.4.1 kernlab_0.9-25
[29] ggvis_0.4.3 caTools_1.17.1 gtable_0.2.0 colorspace_1.2-6
[33] tools_3.2.3 parallel_3.2.3 dplyr_0.5.0 xtable_1.8-2
[37] gtools_3.5.0 backports_1.0.4 Rcpp_0.12.4
I have some longitudinal data from which I'd like to get the predicted means at specified times. The model includes 2 terms, their interaction and a spline term for the time variable. When I try to obtain the predicted means, I get "Error in mm %*% fixef(m4) : non-conformable arguments"
I've used the sleep data set from lmer to illustrate my problem. First, I import the data and create a variable "age" for my interaction
sleep <- as.data.frame(sleepstudy) #get the sleep data
# create fake variable for age with 3 levels
set.seed(1234567)
sleep$age <- as.factor(sample(1:3,length(sleep),rep=TRUE))
Then I run my lmer model
library(lme4)
library(splines)
m4 <- lmer(Reaction ~ Days + ns(Days, df=4) + age + Days:age + (Days | Subject), sleep)
Finally, I create the data and matrix needed to obtain predicted means
#new data frame for predicted means
d <- c(0:9) # make a vector of days = 0 to 9 to obtain predictions for each day
newdat <- as.data.frame(cbind(Days=d, age=rep(c(1:3),length(d))))
newdat$Days <- as.numeric(as.character(newdat$Days))
newdat$age <- as.factor(newdat$age)
# create a matrix
mm<-model.matrix(~Days + ns(Days, df=4) + age + Days:age, newdat)
newdat$pred<-mm%*%fixef(m4)
It's at this point that I get the error:
Error in mm %*% fixef(m4) : non-conformable arguments
I can use predict to get the means
newdat$pred <- predict(m4, newdata=newdat, re.form=NA)
which works fine, but I want to be able to calculate a confidence interval, so I need a conformable matrix.
I read somewhere that the problem may be that lmer creates aliases (I can't find that post). This comment was made with regards to not being able to use effect() for a similar task. I couldn't quite understand how to overcome this problem. Moreover, I recall that post was a little old and hoped the alias problem may no longer be relevant.
If anyone has a suggestion for what I may be doing wrong, I'd appreciate the feedback. Thanks.
There are a couple of things here.
you need to drop columns to make your model matrix commensurate with the fixed effect vector that was actually fitted (i.e., commensurate with the model matrix that was actually used for fitting, after dropping collinear columns)
for additional confusion, you happened to only sample ages 2 and 3 (out of a possible {1,2,3})
I've cleaned up the code a little bit ...
library("lme4")
library("splines")
sleep <- sleepstudy #get the sleep data
set.seed(1234567)
## next line happens to sample only 2 and 3 ...
sleep$age <- as.factor(sample(1:3,length(sleep),rep=TRUE))
length(levels(sleep$age)) ## 2
Fit model:
m4 <- lmer(Reaction ~ Days + ns(Days, df=4) +
age + Days:age + (Days | Subject), sleep)
## message; fixed-effect model matrix is
## rank deficient so dropping 1 column / coefficient
Check fixed effects:
f1 <- fixef(m4)
length(f1) ## 7
f2 <- fixef(m4,add.dropped=TRUE)
length(f2) ## 8
We could use this extended version of the fixed effects (which has an NA value in it), but this would just mess us up by propagating NA values through the computation ...
Check model matrix:
X <- getME(m4,"X")
ncol(X) ## 7
(which.dropped <- attr(getME(m4,"X"),"col.dropped"))
## ns(Days, df = 4)4
## 6
New data frame for predicted means
d <- 0:9
## best to use data.frame() directly, avoid cbind()
## generate age based on *actual* levels in data
newdat <- data.frame(Days=d,
age=factor(rep(levels(sleep$age),length(d))))
Create a matrix:
mm <- model.matrix(formula(m4,fixed.only=TRUE)[-2], newdat)
mm <- mm[,-which.dropped] ## drop redundant columns
## newdat$pred <- mm%*%fixef(m4) ## works now
Added by sianagh: Code to obtain confidence intervals and plot the data:
predFun <- function(x) predict(x,newdata=newdat,re.form=NA)
newdat$pred <- predFun(m4)
bb <- bootMer(m4,
FUN=predFun,
nsim=200)
## nb. this produces an error message on its first run,
## but not on subsequent runs (using the development version of lme4)
bb_ci <- as.data.frame(t(apply(bb$t,2,quantile,c(0.025,0.975))))
names(bb_ci) <- c("lwr","upr")
newdat <- cbind(newdat,bb_ci)
Plot:
plot(Reaction~Days,sleep)
with(newdat,
matlines(Days,cbind(pred,lwr,upr),
col=c("red","green","green"),
lty=2,
lwd=c(3,2,2)))
The error is caused due to the drift component, if you put
allowdrift=FALSE
into your auto.arima prediction it will be fixed.
I am trying to replicate the following script: San Francisco Crime Classification
here is my code:
library(dplyr)
library(ggmap)
library(ggplot2)
library(readr)
library(rjson)
library(RCurl)
library(RJSONIO)
library(jsonlite)
train=jsonlite::fromJSON("/home/felipe/Templates/Archivo de prueba/databritanica.json")
counts <- summarise(group_by(train, Crime_type), Counts=length(Crime_type))
#counts <- counts[order(-counts$Crime_type),]
# This removes the "Other Offenses" category
top12 <- train[train$Crime_type %in% counts$Crime_type[c(1,3:13)],]
map<-get_map(location=c(lon = -2.747770, lat = 53.389499) ,zoom=12,source="osm")
p <- ggmap(map) +
geom_point(data=top12, aes(x=Longitude, y=Latitude, color=factor(Crime_type)), alpha=0.05) +
guides(colour = guide_legend(override.aes = list(alpha=1.0, size=6.0),
title="Type of Crime")) +
scale_colour_brewer(type="qual",palette="Paired") +
ggtitle("Top Crimes in Britain") +
theme_light(base_size=20) +
theme(axis.line=element_blank(),
axis.text.x=element_blank(),
axis.text.y=element_blank(),
axis.ticks=element_blank(),
axis.title.x=element_blank(),
axis.title.y=element_blank())
ggsave("united kingdom_top_crimes_map.png", p, width=14, height=10, units="in")
I am reading the data from a JSON file and try to print points over the map according to the data. Each point is a type of crime that is have been committed, the location of each point depends of two parameters: longitude and latitude.
What is the problem? the points are not being printing. The script generate a new map without the points that is suppose to show.
This is the original map:
And this is the result:
Any ideas??
This a example of the data contain in the JSON file is:
[
{"Month":"2014-05","Longitude":-2.747770,"Latitude":53.389499,"Location":"On or near Cronton Road","LSOA_name":"Halton 001B","Crime_type":"Other theft"},
{"Month":"2014-05","Longitude":-2.799099,"Latitude":53.354676,"Location":"On or near Old Higher Road","LSOA_name":"Halton 008B","Crime_type":"Anti-social behaviour"},
{"Month":"2014-05","Longitude":-2.804451,"Latitude":53.352456,"Location":"On or near Higher Road","LSOA_name":"Halton 008B","Crime_type":"Anti-social behaviour"}
]
Short answer:
Your alpha = 0.05 is making the points practically invisible when plotted on the colorful map background, as mentioned by #aosmith.
Longer answer:
I suggest the following changes to your geom_point:
Increase the alpha to something more reasonable
Increase the size of the points
Optionally, change the shape to one with a background and fill for better visibility
This will require you to change the fill parameter in aes, as well as the scale_color_brewer to scale_fill_brewer
Example:
# Load required packages
library(dplyr)
library(ggplot2)
library(ggmap)
library(jsonlite)
# Example data provided in question, with one manually entered entry with
# Crime_type = "Other Offenses"
'[
{"Month":"2014-05","Longitude":-2.747770,"Latitude":53.389499,"Location":"On or near Cronton Road","LSOA_name":"Halton 001B","Crime_type":"Other theft"},
{"Month":"2014-05","Longitude":-2.799099,"Latitude":53.354676,"Location":"On or near Old Higher Road","LSOA_name":"Halton 008B","Crime_type":"Anti-social behaviour"},
{"Month":"2014-05","Longitude":-2.804451,"Latitude":53.352456,"Location":"On or near Higher Road","LSOA_name":"Halton 008B","Crime_type":"Anti-social behaviour"},
{"Month":"2014-05","Longitude":-2.81,"Latitude":53.36,"Location":"On or near Higher Road","LSOA_name":"Halton 008B","Crime_type":"Other Offenses"}
]' -> example_json
train <- fromJSON(example_json)
# Process the data, the dplyr way
counts <- train %>%
group_by(Crime_type) %>%
summarise(Counts = length(Crime_type))
# This removes the "Other Offenses" category
top12 <- train %>%
filter(Crime_type != "Other Offenses")
# Get the map
map <- get_map(location=c(lon = -2.747770, lat = 53.389499), zoom=12, source="osm")
# Plotting code
p <- ggmap(map) +
# Changes made to geom_point.
# I increased the alpha and size, and I used a shape that has
# a black border and a fill determined by Crime_type.
geom_point(data=top12, aes(x=Longitude, y=Latitude, fill=factor(Crime_type)),
shape = 21, alpha = 0.75, size = 3.5, color = "black") +
guides(fill = guide_legend(override.aes = list(alpha=1.0, size=6.0),
title="Type of Crime")) +
# Changed scale_color_brewer to scale_fill_brewer
scale_fill_brewer(type="qual", palette="Paired") +
ggtitle("Top Crimes in Britain") +
theme_light(base_size=20) +
theme(axis.line=element_blank(),
axis.text.x=element_blank(),
axis.text.y=element_blank(),
axis.ticks=element_blank(),
axis.title.x=element_blank(),
axis.title.y=element_blank())
I have data from GPS log like this : (this data in rows of data frame columns)
{"mAccuracy":20.0,"mAltitude":0.0,"mBearing":0.0,"mElapsedRealtimeNanos":21677339000000,"mExtras":{"networkLocationSource":"cached","networkLocationType":"wifi","noGPSLocation":{"mAccuracy":20.0,"mAltitude":0.0,"mBearing":0.0,"mElapsedRealtimeNanos":21677339000000,"mHasAccuracy":true,"mHasAltitude":false,"mHasBearing":false,"mHasSpeed":false,"mIsFromMockProvider":false,"mLatitude":35.1811956,"mLongitude":126.9104909,"mProvider":"network","mSpeed":0.0,"mTime":1402801381486},"travelState":"stationary"},"mHasAccuracy":true,"mHasAltitude":false,"mHasBearing":false,"mHasSpeed":false,"mIsFromMockProvider":false,"mLatitude":35.1811956,"mLongitude":126.9104909,"mProvider":"network","mSpeed":0.0,"mTime":1402801381486,"timestamp":1402801665.512}
The problem is I only need Latitude and longitude value, so I think i can use substring and sappy for applying to all data in dataframe.
But I am not sure this way is handsome because when i use substring ex: substr("abcdef", 2, 4) so I need to count who many chars from beginning until "mLatitude" , so anybody can give suggestion the fast way to processing it?
Thank you to #mnel for answering question, it's work , but i still have problem
From mnel answer I've created function like this :
fgps <- function(x) {
out <- fromJSON(x)
c(out$mExtras$noGPSLocation$mLatitude,
out$mExtras$noGPSLocation$mLongitude)
}
and then this is my data :
gpsdata <- head(dfallgps[,4],2)
[1] "{\"mAccuracy\":23.128,\"mAltitude\":0.0,\"mBearing\":0.0,\"mElapsedRealtimeNanos\":76437488000000,\"mExtras\":{\"networkLocationSource\":\"cached\",\"networkLocationType\":\"wifi\",\"noGPSLocation\":{\"mAccuracy\":23.128,\"mAltitude\":0.0,\"mBearing\":0.0,\"mElapsedRealtimeNanos\":76437488000000,\"mHasAccuracy\":true,\"mHasAltitude\":false,\"mHasBearing\":false,\"mHasSpeed\":false,\"mIsFromMockProvider\":false,\"mLatitude\":35.1779956,\"mLongitude\":126.9089661,\"mProvider\":\"network\",\"mSpeed\":0.0,\"mTime\":1402894224187},\"travelState\":\"stationary\"},\"mHasAccuracy\":true,\"mHasAltitude\":false,\"mHasBearing\":false,\"mHasSpeed\":false,\"mIsFromMockProvider\":false,\"mLatitude\":35.1779956,\"mLongitude\":126.9089661,\"mProvider\":\"network\",\"mSpeed\":0.0,\"mTime\":1402894224187,\"timestamp\":1402894517.425}"
[2] "{\"mAccuracy\":1625.0,\"mAltitude\":0.0,\"mBearing\":0.0,\"mElapsedRealtimeNanos\":77069916000000,\"mExtras\":{\"networkLocationSource\":\"cached\",\"networkLocationType\":\"cell\",\"noGPSLocation\":{\"mAccuracy\":1625.0,\"mAltitude\":0.0,\"mBearing\":0.0,\"mElapsedRealtimeNanos\":77069916000000,\"mHasAccuracy\":true,\"mHasAltitude\":false,\"mHasBearing\":false,\"mHasSpeed\":false,\"mIsFromMockProvider\":false,\"mLatitude\":35.1811881,\"mLongitude\":126.9084072,\"mProvider\":\"network\",\"mSpeed\":0.0,\"mTime\":1402894857416},\"travelState\":\"stationary\"},\"mHasAccuracy\":true,\"mHasAltitude\":false,\"mHasBearing\":false,\"mHasSpeed\":false,\"mIsFromMockProvider\":false,\"mLatitude\":35.1811881,\"mLongitude\":126.9084072,\"mProvider\":\"network\",\"mSpeed\":0.0,\"mTime\":1402894857416,\"timestamp\":1402894857.519}"
When run sapply why the data still shows in the result not just the results values.
sapply(gpsdata, function(gpsdata) fgps(gpsdata))
{"mAccuracy":23.128,"mAltitude":0.0,"mBearing":0.0,"mElapsedRealtimeNanos":76437488000000,"mExtras":{"networkLocationSource":"cached","networkLocationType":"wifi","noGPSLocation":{"mAccuracy":23.128,"mAltitude":0.0,"mBearing":0.0,"mElapsedRealtimeNanos":76437488000000,"mHasAccuracy":true,"mHasAltitude":false,"mHasBearing":false,"mHasSpeed":false,"mIsFromMockProvider":false,"mLatitude":35.1779956,"mLongitude":126.9089661,"mProvider":"network","mSpeed":0.0,"mTime":1402894224187},"travelState":"stationary"},"mHasAccuracy":true,"mHasAltitude":false,"mHasBearing":false,"mHasSpeed":false,"mIsFromMockProvider":false,"mLatitude":35.1779956,"mLongitude":126.9089661,"mProvider":"network","mSpeed":0.0,"mTime":1402894224187,"timestamp":1402894517.425}
[1,] 35.178
[2,] 126.909
{"mAccuracy":1625.0,"mAltitude":0.0,"mBearing":0.0,"mElapsedRealtimeNanos":77069916000000,"mExtras":{"networkLocationSource":"cached","networkLocationType":"cell","noGPSLocation":{"mAccuracy":1625.0,"mAltitude":0.0,"mBearing":0.0,"mElapsedRealtimeNanos":77069916000000,"mHasAccuracy":true,"mHasAltitude":false,"mHasBearing":false,"mHasSpeed":false,"mIsFromMockProvider":false,"mLatitude":35.1811881,"mLongitude":126.9084072,"mProvider":"network","mSpeed":0.0,"mTime":1402894857416},"travelState":"stationary"},"mHasAccuracy":true,"mHasAltitude":false,"mHasBearing":false,"mHasSpeed":false,"mIsFromMockProvider":false,"mLatitude":35.1811881,"mLongitude":126.9084072,"mProvider":"network","mSpeed":0.0,"mTime":1402894857416,"timestamp":1402894857.519}
[1,] 35.18119
[2,] 126.90841
I want the result looks like :
[1] 35.178 126.909
[2] 35.18119 126.90841
Thank you
It would appear that your data is in JSON format. Therefore, use a RJSONIO::fromJSON to read the file.
E.g.:
txt <- "{\"mAccuracy\":20.0,\"mAltitude\":0.0,\"mBearing\":0.0,\"mElapsedRealtimeNanos\":21677339000000,\"mExtras\":{\"networkLocationSource\":\"cached\",\"networkLocationType\":\"wifi\",\"noGPSLocation\":{\"mAccuracy\":20.0,\"mAltitude\":0.0,\"mBearing\":0.0,\"mElapsedRealtimeNanos\":21677339000000,\"mHasAccuracy\":true,\"mHasAltitude\":false,\"mHasBearing\":false,\"mHasSpeed\":false,\"mIsFromMockProvider\":false,\"mLatitude\":35.1811956,\"mLongitude\":126.9104909,\"mProvider\":\"network\",\"mSpeed\":0.0,\"mTime\":1402801381486},\"travelState\":\"stationary\"},\"mHasAccuracy\":true,\"mHasAltitude\":false,\"mHasBearing\":false,\"mHasSpeed\":false,\"mIsFromMockProvider\":false,\"mLatitude\":35.1811956,\"mLongitude\":126.9104909,\"mProvider\":\"network\",\"mSpeed\":0.0,\"mTime\":1402801381486,\"timestamp\":1402801665.512}"
Then process:
library(RJSONIO)
out <- fromJSON(txt)
out$$mLongitude
#[1] 126.9105
out$mLatitude
#[1] 35.1812
# to process multiple values
tt <- rep(txt,2)
myData <- lapply(tt, fromJSON)
latlong <- do.call(rbind,lapply(myData, `[` ,c('mLatitude','mLongitude')))
# or using rbind list
library(data.table)
latlong <- rbindlist(lapply(myData, `[` ,c('mLatitude','mLongitude')))