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# This script was originally copied from | ||
# https://github.com/ShimmerEngineering/Verisense-Toolbox/tree/master/Verisense_step_algorithm | ||
# where it included the following software license: | ||
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# Copyright (c) 2020 Shimmer | ||
# | ||
# Permission is hereby granted, free of charge, to any person obtaining a copy | ||
# of this software and associated documentation files (the "Software"), to deal | ||
# in the Software without restriction, including without limitation the rights | ||
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
# copies of the Software, and to permit persons to whom the Software is | ||
# furnished to do so, subject to the following conditions: | ||
# | ||
# The above copyright notice and this permission notice shall be included in all | ||
# copies or substantial portions of the Software. | ||
# | ||
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | ||
# SOFTWARE. | ||
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verisense_count_steps <- function(input_data = runif(500, min = -1.5, max = 1.5), | ||
coeffs = c(0, 0, 0)) { | ||
# by Matthew R Patterson, mpatterson@shimmersensing.com | ||
## Find peaks of RMS acceleration signal according to Gu et al, 2017 method | ||
# This method is based off finding peaks in the summed and squared acceleration signal | ||
# and then using multiple thresholds to determine if each peak is a step or an artefact. | ||
# An additional magnitude threshold was added to the algorithm to prevent false positives | ||
# in free living data. | ||
# | ||
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# # TO BE USED WITH GGIR AS FOLLOWS: | ||
# | ||
# source("your_file_path/verisense_count_steps.R") | ||
# myfun = list(FUN = verisense_count_steps, | ||
# parameters = c(4, 4, 20, -1.0, 4, 4, 0.01, 1.25), # updated based on Rowlands et al Stepping up with GGIR 2022 | ||
# expected_sample_rate = 15, | ||
# expected_unit = "g", | ||
# colnames = c("step_count"), | ||
# outputres = 1, | ||
# minlength = 1, | ||
# outputtype = "numeric", | ||
# aggfunction = sum, | ||
# timestamp = F, | ||
# reporttype = "event") | ||
# | ||
# GGIR(myfun = myfun, ...) | ||
# | ||
# See also https://wadpac.github.io/GGIR/articles/ExternalFunction.html | ||
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# returns sample location of each step | ||
fs = 15 # temporary for now, this is manually set | ||
acc <- sqrt(input_data[, 1]^2 + input_data[, 2]^2 + input_data[, 3]^2) | ||
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if (sd(acc) < 0.025) { | ||
# acceleration too low, no steps | ||
num_seconds = round(length(acc) / fs) | ||
steps_per_sec = rep(0, num_seconds) | ||
} else { | ||
# Search for steps | ||
# Thresholds | ||
k <- coeffs[[1]] | ||
period_min <- coeffs[[2]] | ||
period_max <- coeffs[[3]] | ||
sim_thres <- coeffs[[4]] # similarity threshold | ||
cont_win_size <- coeffs[[5]] # continuity window size | ||
cont_thres <- coeffs[[6]] # continuity threshold | ||
var_thres <- coeffs[[7]] # variance threshold | ||
mag_thres <- coeffs[[8]] | ||
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# find the peak rms value is every range of k | ||
half_k <- round(k / 2) | ||
segments <- floor(length(acc) / k) | ||
peak_info <- matrix(NA, nrow = segments, ncol = 5) | ||
# peak_info[,1] - peak location | ||
# peak_info[,2] - acc magnitude | ||
# peak_info[,3] - periodicity (samples) | ||
# peak_info[,4] - similarity | ||
# peak_info[,5] - continuity | ||
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# for each segment find the peak location | ||
for (i in 1:segments) { | ||
start_idx <- (i - 1) * k + 1 | ||
end_idx <- start_idx + (k - 1) | ||
tmp_loc_a <- which.max(acc[start_idx:end_idx]) | ||
tmp_loc_b <- (i - 1) * k + tmp_loc_a | ||
# only save if this is a peak value in range of -k/2:+K/2 | ||
start_idx_ctr <- tmp_loc_b - half_k | ||
if (start_idx_ctr < 1) { | ||
start_idx_ctr <- 1 | ||
} | ||
end_idx_ctr <- tmp_loc_b + half_k | ||
if (end_idx_ctr > length(acc)) { | ||
end_idx_ctr <- length(acc) | ||
} | ||
check_loc <- which.max(acc[start_idx_ctr:end_idx_ctr]) | ||
if (check_loc == (half_k + 1)) { | ||
peak_info[i, 1] <- tmp_loc_b | ||
peak_info[i, 2] <- max(acc[start_idx:end_idx]) | ||
} | ||
} | ||
peak_info <- peak_info[is.na(peak_info[, 1]) != TRUE, ] # get rid of na rows | ||
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# filter peak_info[,2] based on mag_thres | ||
peak_info <- peak_info[peak_info[, 2] > mag_thres, ] | ||
if (length(peak_info) > 10) { | ||
# there must be at least two steps | ||
num_peaks <- length(peak_info[, 1]) | ||
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no_steps = FALSE | ||
if (num_peaks > 2) { | ||
# Calculate Features (periodicity, similarity, continuity) | ||
peak_info[1:(num_peaks - 1), 3] <- diff(peak_info[, 1]) # calculate periodicity | ||
peak_info <- peak_info[peak_info[, 3] > period_min, ] # filter peaks based on period_min | ||
peak_info <- peak_info[peak_info[, 3] < period_max, ] # filter peaks based on period_max | ||
} else { | ||
no_steps = TRUE | ||
} | ||
} else { | ||
no_steps = TRUE | ||
} | ||
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if (length(peak_info) == 0 || | ||
length(peak_info) == sum(is.na(peak_info)) || no_steps == TRUE) { | ||
# no steps found | ||
num_seconds = round(length(acc) / fs) | ||
steps_per_sec = rep(0, num_seconds) | ||
} else { | ||
# calculate similarity | ||
num_peaks <- length(peak_info[, 1]) | ||
peak_info[1:(num_peaks - 2), 4] <- -abs(diff(peak_info[, 2], 2)) # calculate similarity | ||
peak_info <- peak_info[peak_info[, 4] > sim_thres, , drop = FALSE] # filter based on sim_thres | ||
peak_info <- peak_info[is.na(peak_info[, 1]) != TRUE, , drop = FALSE] # previous statement can result in an NA in col-1 | ||
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# calculate continuity | ||
if (length(peak_info[, 3]) > 5) { | ||
end_for <- length(peak_info[, 3]) - 1 | ||
for (i in cont_thres:end_for) { | ||
# for each bw peak period calculate acc var | ||
v_count <- 0 # count how many windows were over the variance threshold | ||
for (x in 1:cont_thres) { | ||
if (var(acc[peak_info[i - x + 1, 1]:peak_info[i - x + 2, 1]]) > var_thres) { | ||
v_count = v_count + 1 | ||
} | ||
} | ||
if (v_count >= cont_win_size) { | ||
peak_info[i, 5] <- 1 # set continuity to 1, otherwise, 0 | ||
} else { | ||
peak_info[i, 5] <- 0 | ||
} | ||
} | ||
} | ||
peak_info <- peak_info[peak_info[, 5] == 1, 1] # continuity test - only keep locations after this | ||
peak_info <- peak_info[is.na(peak_info) != TRUE] # previous statement can result in an NA in col-1 | ||
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if (length(peak_info) == 0) { | ||
# no steps found | ||
num_seconds = round(length(acc) / fs) | ||
steps_per_sec = rep(0, num_seconds) | ||
} else { | ||
# debug plot | ||
# is_plot = F | ||
# if (is_plot) { | ||
# library(ggplot2) | ||
# library(plotly) | ||
# acc.df <- data.frame(acc=acc, det_step=integer(length(acc))) | ||
# acc.df$det_step[peak_info] <- 1 # to plot annotations, prepare a 0/1 column on dataframe | ||
# acc.df$idx <- as.numeric(row.names(acc.df)) | ||
# pl <- ggplot(data=acc.df,aes(x=idx,y=acc)) | ||
# pl2 <- pl + geom_line() | ||
# pl3 <- pl2 + geom_point(data=subset(acc.df,det_step==1),aes(x=idx,y=acc),color='red',size=1,alpha=0.7) | ||
# pl4 <- ggplotly(pl3) | ||
# print(pl4) | ||
# } | ||
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# for GGIR, output the number of steps in 1 second chunks | ||
start_idx_vec <- seq(from = 1, | ||
to = length(acc), | ||
by = fs) | ||
steps_per_sec <- table(factor( | ||
findInterval(peak_info, start_idx_vec), | ||
levels = seq_along(start_idx_vec) | ||
)) | ||
steps_per_sec <- as.numeric(steps_per_sec) | ||
} | ||
} | ||
} | ||
return(steps_per_sec) | ||
} |
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