A Kagi chart is a Japanese charting technique that displays price movements using vertical lines of varying thickness. Unlike time-based charts, Kagi charts change direction only when price moves by a significant amount (the reversal threshold), effectively filtering out market noise. Thick lines (yang) indicate uptrends when price exceeds previous highs, while thin lines (yin) show downtrends when price falls below previous lows, making trend identification intuitive.
#' anyplot.ai
#' kagi-basic: Basic Kagi Chart
#' Library: ggplot2 3.5.1 | R 4.4.1
#' Quality: 95/100 | Created: 2026-05-17
library(ggplot2)
library(dplyr)
library(tibble)
library(ragg)
set.seed(42)
# --- Theme tokens -----------------------------------------------------------
THEME <- Sys.getenv("ANYPLOT_THEME", "light")
PAGE_BG <- if (THEME == "light") "#FAF8F1" else "#1A1A17"
INK <- if (THEME == "light") "#1A1A17" else "#F0EFE8"
INK_SOFT <- if (THEME == "light") "#4A4A44" else "#B8B7B0"
# Kagi-specific colors: yang (uptrend) uses brand green, yin (downtrend) uses vermillion
COLOR_YANG <- "#009E73" # Okabe-Ito position 1 — uptrend
COLOR_YIN <- "#AE3030" # imprint red — downtrend
# --- Generate price data -----------------------------------------------------
# Daily closing prices over ~6 months with realistic volatility
n_days <- 150
dates <- seq(as.Date("2025-10-01"), by = "day", length.out = n_days)
# Random walk with slight upward drift
price_changes <- rnorm(n_days, mean = 0.003, sd = 0.02)
prices <- 100 * exp(cumsum(price_changes))
df_raw <- tibble::tibble(
date = dates,
close = prices
)
# --- Calculate Kagi segments -------------------------------------------------
# Reversal threshold: 4% of current price
reversal_pct <- 0.04
kagi_data <- list()
line_idx <- 0
direction <- NA # "up" or "down"
line_start_idx <- 1
line_start_price <- df_raw$close[1]
last_reversal_price <- df_raw$close[1]
for (i in 2:nrow(df_raw)) {
price <- df_raw$close[i]
# Determine trend direction based on reversal threshold
if (is.na(direction)) {
# Initial direction: assume uptrend if price goes up
if (price > line_start_price * (1 + reversal_pct)) {
direction <- "up"
last_reversal_price <- line_start_price
} else if (price < line_start_price * (1 - reversal_pct)) {
direction <- "down"
last_reversal_price <- line_start_price
}
} else if (direction == "up") {
# In uptrend, check if price reverses down
if (price < last_reversal_price * (1 - reversal_pct)) {
# Reversal: end current up line, start down line
line_idx <- line_idx + 1
kagi_data[[line_idx]] <- tibble::tibble(
line_id = line_idx,
line_num = line_idx,
price_start = line_start_price,
price_end = last_reversal_price,
idx_start = line_start_idx,
idx_end = i - 1,
trend = "up"
)
direction <- "down"
line_start_price <- last_reversal_price
line_start_idx <- i - 1
last_reversal_price <- price
} else if (price > last_reversal_price) {
# Continue up, update high
last_reversal_price <- price
}
} else { # direction == "down"
# In downtrend, check if price reverses up
if (price > last_reversal_price * (1 + reversal_pct)) {
# Reversal: end current down line, start up line
line_idx <- line_idx + 1
kagi_data[[line_idx]] <- tibble::tibble(
line_id = line_idx,
line_num = line_idx,
price_start = line_start_price,
price_end = last_reversal_price,
idx_start = line_start_idx,
idx_end = i - 1,
trend = "down"
)
direction <- "up"
line_start_price <- last_reversal_price
line_start_idx <- i - 1
last_reversal_price <- price
} else if (price < last_reversal_price) {
# Continue down, update low
last_reversal_price <- price
}
}
}
# Add final segment
if (!is.na(direction)) {
line_idx <- line_idx + 1
kagi_data[[line_idx]] <- tibble::tibble(
line_id = line_idx,
line_num = line_idx,
price_start = line_start_price,
price_end = last_reversal_price,
idx_start = line_start_idx,
idx_end = nrow(df_raw),
trend = direction
)
}
kagi_df <- bind_rows(kagi_data)
# --- Create line segments for plotting ----------------------------------------
segments <- list()
seg_idx <- 1
for (i in 1:nrow(kagi_df)) {
segment <- kagi_df[i, ]
# Create vertical line segment
segments[[seg_idx]] <- tibble::tibble(
x = segment$line_num,
y_start = segment$price_start,
y_end = segment$price_end,
trend = segment$trend,
color = if_else(segment$trend == "up", COLOR_YANG, COLOR_YIN),
width = if_else(segment$trend == "up", 1.2, 0.6)
)
seg_idx <- seg_idx + 1
# Add horizontal segment (shoulder/waist) connecting to next line
if (i < nrow(kagi_df)) {
next_start <- kagi_df$price_start[i + 1]
segments[[seg_idx]] <- tibble::tibble(
x = c(segment$line_num, segment$line_num + 0.5),
y_start = c(segment$price_end, segment$price_end),
y_end = c(segment$price_end, segment$price_end),
trend = NA,
color = INK_SOFT,
width = 0.3
)
seg_idx <- seg_idx + 1
}
}
# --- Plot -------------------------------------------------------------------
# Build base data for geom_segment calls
plot_lines <- list()
# Draw vertical lines
for (i in 1:nrow(kagi_df)) {
segment <- kagi_df[i, ]
color <- if_else(segment$trend == "up", COLOR_YANG, COLOR_YIN)
width <- if_else(segment$trend == "up", 1.2, 0.6)
plot_lines[[i]] <- tibble::tibble(
x = segment$line_num,
xend = segment$line_num,
y = segment$price_start,
yend = segment$price_end,
trend = segment$trend,
color = color,
linewidth = width
)
}
plot_data <- bind_rows(plot_lines)
p <- ggplot() +
geom_segment(
data = plot_data,
aes(x = x, xend = xend, y = y, yend = yend, color = trend, linewidth = trend),
show.legend = FALSE
) +
scale_color_manual(values = c("up" = COLOR_YANG, "down" = COLOR_YIN)) +
scale_linewidth_manual(values = c("up" = 1.2, "down" = 0.6)) +
labs(
title = "kagi-basic · ggplot2 · anyplot.ai",
x = "Line Index",
y = "Price"
) +
theme_minimal(base_size = 14) +
theme(
plot.background = element_rect(fill = PAGE_BG, color = PAGE_BG),
panel.background = element_rect(fill = PAGE_BG, color = NA),
panel.grid.major = element_line(color = INK_SOFT, linewidth = 0.3),
panel.grid.minor = element_blank(),
axis.title = element_text(color = INK, size = 20),
axis.text = element_text(color = INK_SOFT, size = 16),
plot.title = element_text(color = INK, size = 24, face = "plain")
)
# --- Save -------------------------------------------------------------------
ggsave(
filename = sprintf("plot-%s.png", THEME),
plot = p,
device = ragg::agg_png,
width = 16,
height = 9,
units = "in",
dpi = 300
)
Part of Basic Kagi Chart on anyplot.ai.