feat(ggplot2): implement indicator-ema

plots/indicator-ema/implementations/r/ggplot2.R

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+#' anyplot.ai
+#' indicator-ema: Exponential Moving Average (EMA) Indicator Chart
+#' Library: ggplot2 3.5.1 | R 4.4.1
+#' Quality: 92/100 | Created: 2026-05-19
+
+library(ggplot2)
+library(scales)
+library(tidyr)
+library(ragg)
+
+set.seed(42)
+
+# Theme tokens
+THEME       <- Sys.getenv("ANYPLOT_THEME", "light")
+PAGE_BG     <- if (THEME == "light") "#FAF8F1" else "#1A1A17"
+ELEVATED_BG <- if (THEME == "light") "#FFFDF6" else "#242420"
+INK         <- if (THEME == "light") "#1A1A17" else "#F0EFE8"
+INK_SOFT    <- if (THEME == "light") "#4A4A44" else "#B8B7B0"
+
+OKABE_ITO <- c(
+    "Price"    = "#009E73",
+    "EMA (12)" = "#D55E00",
+    "EMA (26)" = "#0072B2"
+)
+
+# Data
+n_days <- 180
+dates  <- seq.Date(as.Date("2024-01-02"), by = "day", length.out = n_days)
+close  <- 150 * cumprod(1 + rnorm(n_days, mean = 0.0005, sd = 0.018))
+
+# Inline EMA via Reduce — no helper function needed
+k12   <- 2 / (12 + 1)
+k26   <- 2 / (26 + 1)
+ema12 <- Reduce(function(e, x) x * k12 + e * (1 - k12), close, accumulate = TRUE)
+ema26 <- Reduce(function(e, x) x * k26 + e * (1 - k26), close, accumulate = TRUE)
+
+df <- data.frame(date = dates, close = close, ema12 = ema12, ema26 = ema26)
+
+# Detect EMA crossovers (sign change in ema12 - ema26)
+diff_ema   <- df$ema12 - df$ema26
+cross_idx  <- which(diff(sign(diff_ema)) != 0) + 1
+crossovers <- df[cross_idx, , drop = FALSE]
+
+# Long form for idiomatic ggplot2 multi-series mapping
+df_long <- pivot_longer(df, cols = c(close, ema12, ema26),
+                        names_to = "series", values_to = "price")
+df_long$series <- factor(df_long$series,
+    levels = c("close", "ema12", "ema26"),
+    labels = c("Price", "EMA (12)", "EMA (26)"))
+
+# Plot
+p <- ggplot(df_long, aes(x = date, y = price, color = series)) +
+    geom_vline(data = crossovers, aes(xintercept = date),
+               color = INK_SOFT, linetype = "dashed",
+               linewidth = 0.4, alpha = 0.7) +
+    geom_line(aes(linewidth = series, alpha = series)) +
+    geom_point(data = crossovers, aes(x = date, y = ema12),
+               shape = 21, size = 4, fill = PAGE_BG,
+               color = OKABE_ITO[["EMA (12)"]], stroke = 1.5,
+               inherit.aes = FALSE) +
+    scale_color_manual(name = NULL, values = OKABE_ITO,
+                       breaks = c("Price", "EMA (12)", "EMA (26)")) +
+    scale_linewidth_manual(
+        values = c("Price" = 1.5, "EMA (12)" = 1.1, "EMA (26)" = 1.1),
+        guide  = "none") +
+    scale_alpha_manual(
+        values = c("Price" = 0.80, "EMA (12)" = 1.0, "EMA (26)" = 1.0),
+        guide  = "none") +
+    scale_x_date(date_labels = "%b %Y", date_breaks = "2 months") +
+    scale_y_continuous(labels = dollar_format()) +
+    labs(
+        title = "Tech Stock EMA · indicator-ema · r · ggplot2 · anyplot.ai",
+        x     = "Date",
+        y     = "Closing Price (USD)"
+    ) +
+    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.y = element_line(color = INK_SOFT,   linewidth = 0.3),
+        panel.grid.major.x = element_blank(),
+        panel.grid.minor   = element_blank(),
+        panel.border       = element_blank(),
+        axis.title         = element_text(color = INK,        size = 20),
+        axis.text          = element_text(color = INK_SOFT,   size = 16),
+        axis.line          = element_line(color = INK_SOFT,   linewidth = 0.5),
+        plot.title         = element_text(color = INK,        size = 24, face = "bold"),
+        legend.background  = element_rect(fill = ELEVATED_BG, color = INK_SOFT),
+        legend.text        = element_text(color = INK_SOFT,   size = 16),
+        legend.key         = element_rect(fill = ELEVATED_BG, color = NA),
+        legend.position    = "bottom",
+        plot.margin        = margin(20, 20, 20, 20, unit = "pt")
+    )
+
+ggsave(
+    filename = sprintf("plot-%s.png", THEME),
+    plot     = p,
+    device   = ragg::agg_png,
+    width    = 16,
+    height   = 9,
+    units    = "in",
+    dpi      = 300
+)

plots/indicator-ema/metadata/r/ggplot2.yaml

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+library: ggplot2
+language: r
+specification_id: indicator-ema
+created: '2026-05-19T05:00:14Z'
+updated: '2026-05-19T05:20:44Z'
+generated_by: claude-sonnet
+workflow_run: 26077083850
+issue: 3652
+language_version: 4.4.1
+library_version: 3.5.1
+preview_url_light: https://storage.googleapis.com/anyplot-images/plots/indicator-ema/r/ggplot2/plot-light.png
+preview_url_dark: https://storage.googleapis.com/anyplot-images/plots/indicator-ema/r/ggplot2/plot-dark.png
+preview_html_light: null
+preview_html_dark: null
+quality_score: 92
+review:
+  strengths:
+  - Complete theme-adaptive chrome with zero dark-on-dark failures
+  - Idiomatic ggplot2 long-format pattern for clean multi-series mapping
+  - Technically correct EMA via Reduce with proper exponential smoothing factor
+  - Crossover detection and visualization adds real chart value
+  - Alpha and linewidth differentiation creates visual hierarchy between price and
+    EMA lines
+  weaknesses:
+  - DE-01 could be elevated with typography polish or a focal annotation at the most
+    significant crossover
+  - Frequent crossover dashed verticals add visual noise; limiting to significant
+    crossovers would improve storytelling
+  image_description: |-
+    Light render (plot-light.png):
+      Background: Warm off-white #FAF8F1 — correct light surface
+      Chrome: Title "Tech Stock EMA · indicator-ema · r · ggplot2 · anyplot.ai" in bold dark text clearly readable; axis labels "Closing Price (USD)" and "Date" readable; tick labels ($140-$180, Feb/Apr/Jun 2024) readable in INK_SOFT gray; legend box with subtle border at bottom showing Price/EMA(12)/EMA(26)
+      Data: Three lines — Price in teal #009E73 (slightly transparent), EMA(12) in orange #D55E00, EMA(26) in blue #0072B2; dashed vertical gray crossover lines; open circles at crossover points on EMA(12)
+      Legibility verdict: PASS — all text clearly readable against light background
+
+    Dark render (plot-dark.png):
+      Background: Warm near-black #1A1A17 — correct dark surface
+      Chrome: Title and axis labels rendered in light off-white (#F0EFE8); tick labels in soft light gray (#B8B7B0); legend box using elevated dark background #242420 with light text — all readable
+      Data: Data line colors identical to light render (teal #009E73, orange #D55E00, blue #0072B2); crossover markers and dashed verticals adapt to lighter chrome
+      Legibility verdict: PASS — no dark-on-dark failures; all text clearly legible against dark background
+  criteria_checklist:
+    visual_quality:
+      score: 30
+      max: 30
+      items:
+      - id: VQ-01
+        name: Text Legibility
+        score: 8
+        max: 8
+        passed: true
+        comment: Title 24pt, axis labels 20pt, tick labels 16pt, legend 16pt all explicitly
+          set; readable in both themes
+      - id: VQ-02
+        name: No Overlap
+        score: 6
+        max: 6
+        passed: true
+        comment: No text collisions; line overlaps are inherent to EMA overlay chart
+          type
+      - id: VQ-03
+        name: Element Visibility
+        score: 6
+        max: 6
+        passed: true
+        comment: Lines well-sized at linewidth 1.1-1.5; crossover markers visible
+          at size=4
+      - id: VQ-04
+        name: Color Accessibility
+        score: 2
+        max: 2
+        passed: true
+        comment: Okabe-Ito teal/orange/blue is CVD-safe; adequate contrast in both
+          themes
+      - id: VQ-05
+        name: Layout & Canvas
+        score: 4
+        max: 4
+        passed: true
+        comment: Plot fills canvas well; 20pt margins; legend well-positioned at bottom
+      - id: VQ-06
+        name: Axis Labels & Title
+        score: 2
+        max: 2
+        passed: true
+        comment: Closing Price (USD) with units; Date appropriate for x-axis
+      - id: VQ-07
+        name: Palette Compliance
+        score: 2
+        max: 2
+        passed: true
+        comment: 'Price=#009E73, EMA(12)=#D55E00, EMA(26)=#0072B2; backgrounds #FAF8F1/#1A1A17;
+          data colors identical across themes'
+    design_excellence:
+      score: 13
+      max: 20
+      items:
+      - id: DE-01
+        name: Aesthetic Sophistication
+        score: 5
+        max: 8
+        passed: true
+        comment: 'Above generic defaults: alpha differentiation, hollow crossover
+          markers; intentional design choices but not publication-grade'
+      - id: DE-02
+        name: Visual Refinement
+        score: 4
+        max: 6
+        passed: true
+        comment: L-shaped frame via axis.line + panel.border blank; y-only major grid;
+          no minor grid; semantic crossover verticals
+      - id: DE-03
+        name: Data Storytelling
+        score: 4
+        max: 6
+        passed: true
+        comment: Crossover highlights create clear focal points; alpha/linewidth hierarchy
+          keeps EMAs prominent
+    spec_compliance:
+      score: 15
+      max: 15
+      items:
+      - id: SC-01
+        name: Plot Type
+        score: 5
+        max: 5
+        passed: true
+        comment: Correct EMA overlay chart with price + two EMA periods
+      - id: SC-02
+        name: Required Features
+        score: 4
+        max: 4
+        passed: true
+        comment: Price line prominent; EMAs overlaid; distinct colors; thinner EMAs;
+          legend labels; crossover highlighting
+      - id: SC-03
+        name: Data Mapping
+        score: 3
+        max: 3
+        passed: true
+        comment: Date on x, closing price on y; all series visible across 180 trading
+          days
+      - id: SC-04
+        name: Title & Legend
+        score: 3
+        max: 3
+        passed: true
+        comment: Title matches {Descriptive}·{spec-id}·r·ggplot2·anyplot.ai format;
+          legend labels correct
+    data_quality:
+      score: 15
+      max: 15
+      items:
+      - id: DQ-01
+        name: Feature Coverage
+        score: 6
+        max: 6
+        passed: true
+        comment: Price volatility, EMA smoothing, crossovers, uptrend and downtrend
+          phases all present
+      - id: DQ-02
+        name: Realistic Context
+        score: 5
+        max: 5
+        passed: true
+        comment: Tech Stock EMA neutral trading scenario; standard periods 12/26;
+          plausible price action
+      - id: DQ-03
+        name: Appropriate Scale
+        score: 4
+        max: 4
+        passed: true
+        comment: Starting price $150, range $135-$180; daily drift/volatility realistic
+          for tech stocks
+    code_quality:
+      score: 10
+      max: 10
+      items:
+      - id: CQ-01
+        name: KISS Structure
+        score: 3
+        max: 3
+        passed: true
+        comment: 'Linear flow: imports → tokens → data → EMA → crossovers → reshape
+          → plot → save'
+      - id: CQ-02
+        name: Reproducibility
+        score: 2
+        max: 2
+        passed: true
+        comment: set.seed(42) present
+      - id: CQ-03
+        name: Clean Imports
+        score: 2
+        max: 2
+        passed: true
+        comment: ggplot2, scales, tidyr, ragg all actively used
+      - id: CQ-04
+        name: Code Elegance
+        score: 2
+        max: 2
+        passed: true
+        comment: Idiomatic Reduce for inline EMA; pivot_longer for reshaping; named
+          color vector
+      - id: CQ-05
+        name: Output & API
+        score: 1
+        max: 1
+        passed: true
+        comment: sprintf plot-%s.png → plot-light/dark.png; ragg::agg_png device
+    library_mastery:
+      score: 9
+      max: 10
+      items:
+      - id: LM-01
+        name: Idiomatic Usage
+        score: 5
+        max: 5
+        passed: true
+        comment: 'Exemplary: long-format data, named aesthetic vectors, scale_linewidth/alpha_manual
+          with guide=none, multi-dataset geoms with inherit.aes=FALSE'
+      - id: LM-02
+        name: Distinctive Features
+        score: 4
+        max: 5
+        passed: true
+        comment: Grammar-driven multi-aesthetic scaling, multi-dataset geom layering,
+          factor levels for legend ordering — distinctively ggplot2
+  verdict: APPROVED
+impl_tags:
+  dependencies:
+  - scales
+  - tidyr
+  - ragg
+  techniques:
+  - layer-composition
+  patterns:
+  - data-generation
+  - wide-to-long
+  dataprep:
+  - time-series
+  styling:
+  - alpha-blending