diff --git a/README.md b/README.md
index e11818a..e947cdf 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ RやPythonのコード（具体的なコンピュータプログラム）の読
 本書には，次の三つの特徴があります．
 
 1. 第1部「データサイエンスの準備」で，準備に時間をかけています．
-1. ほぼ全ての例をコードに基づいて説明しています．本書掲載のコードはサポートサイト（[ここ](#コード)）でも公開しています（使用方法は2.6節を参照）．ただし，コードは自分で入力して実行することを勧めます．
+1. ほぼ全ての例をコードに基づいて説明しています．本書掲載のコードはサポートサイト（[ここ](#コード)）でも公開しています（使用方法は2.6節を参照）．
 1. 第2部「機械学習」では，ほぼ全ての課題をRとPythonで解決し，同じ結果を得ることを試みています．
 
 ## 目次
diff --git a/code/Python-notebook/ch08/08-colab.ipynb b/code/Python-notebook/ch08/08-colab.ipynb
index 5ccc1a6..f6cab75 100644
--- a/code/Python-notebook/ch08/08-colab.ipynb
+++ b/code/Python-notebook/ch08/08-colab.ipynb
@@ -4,23 +4,8 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# 08"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": [
-    "# Google Colaboratoryの環境設定\n",
-    "!pip install -U scikit-learn | tail -n 1"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
+    "# 08\n",
+    "\n",
     "## 8.1 ブドウの生育条件とワインの価格"
    ]
   },
diff --git a/code/Python-notebook/ch10/10-colab.ipynb b/code/Python-notebook/ch10/10-colab.ipynb
index 1c2e061..56da421 100644
--- a/code/Python-notebook/ch10/10-colab.ipynb
+++ b/code/Python-notebook/ch10/10-colab.ipynb
@@ -4,23 +4,8 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# 10"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": [
-    "# Google Colaboratoryの環境設定\n",
-    "!pip install -U scikit-learn | tail -n 1"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
+    "# 10\n",
+    "\n",
     "## 10.1 2値分類の性能指標\n",
     "\n",
     "### 10.1.1 陽性と陰性"
diff --git a/code/R-notebook/ch03/03-colab.ipynb b/code/R-notebook/ch03/03-colab.ipynb
index 2ec5367..1b169c0 100644
--- a/code/R-notebook/ch03/03-colab.ipynb
+++ b/code/R-notebook/ch03/03-colab.ipynb
@@ -14,6 +14,7 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
+    "options(Ncpus = 2)\n",
     "install.packages(c(\"furrr\", \"keras\", \"proxy\"))"
    ]
   },
diff --git a/code/R-notebook/ch04/04-colab.ipynb b/code/R-notebook/ch04/04-colab.ipynb
index 892c310..b59bc4f 100644
--- a/code/R-notebook/ch04/04-colab.ipynb
+++ b/code/R-notebook/ch04/04-colab.ipynb
@@ -14,6 +14,7 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
+    "options(Ncpus = 2)\n",
     "install.packages(c(\"exactci\", \"ggmosaic\", \"pastecs\", \"psych\", \"vcd\"))"
    ]
   },
diff --git a/code/R-notebook/ch05/05-colab.ipynb b/code/R-notebook/ch05/05-colab.ipynb
index 6a4f35d..35c4830 100644
--- a/code/R-notebook/ch05/05-colab.ipynb
+++ b/code/R-notebook/ch05/05-colab.ipynb
@@ -14,6 +14,7 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
+    "options(Ncpus = 2)\n",
     "install.packages(\"caret\")"
    ]
   },
diff --git a/code/R-notebook/ch07/07-colab.ipynb b/code/R-notebook/ch07/07-colab.ipynb
index 1167ea7..c7ea61a 100644
--- a/code/R-notebook/ch07/07-colab.ipynb
+++ b/code/R-notebook/ch07/07-colab.ipynb
@@ -14,6 +14,7 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
+    "options(Ncpus = 2)\n",
     "install.packages(c(\"caret\", \"doParallel\", \"pastecs\"))"
    ]
   },
diff --git a/code/R-notebook/ch08/08-colab.ipynb b/code/R-notebook/ch08/08-colab.ipynb
index 17e6136..4ba249e 100644
--- a/code/R-notebook/ch08/08-colab.ipynb
+++ b/code/R-notebook/ch08/08-colab.ipynb
@@ -14,6 +14,7 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
+    "options(Ncpus = 2)\n",
     "install.packages(c(\"caret\", \"ggfortify\", \"glmnet\", \"glmnetUtils\", \"leaps\", \"neuralnet\", \"psych\"))"
    ]
   },
diff --git a/code/R-notebook/ch09/09-colab.ipynb b/code/R-notebook/ch09/09-colab.ipynb
index 8057c91..6ecd7af 100644
--- a/code/R-notebook/ch09/09-colab.ipynb
+++ b/code/R-notebook/ch09/09-colab.ipynb
@@ -14,6 +14,7 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
+    "options(Ncpus = 2)\n",
     "install.packages(c(\"caret\", \"e1071\", \"furrr\", \"psych\", \"randomForest\", \"rpart.plot\", \"xgboost\"))"
    ]
   },
diff --git a/code/R-notebook/ch10/10-colab.ipynb b/code/R-notebook/ch10/10-colab.ipynb
index d41f68c..9726b7b 100644
--- a/code/R-notebook/ch10/10-colab.ipynb
+++ b/code/R-notebook/ch10/10-colab.ipynb
@@ -14,6 +14,7 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
+    "options(Ncpus = 2)\n",
     "install.packages(c(\"caret\", \"e1071\", \"PRROC\", \"rpart.plot\"))"
    ]
   },
diff --git a/code/R-notebook/ch11/11-colab.ipynb b/code/R-notebook/ch11/11-colab.ipynb
index 2260d3c..0ebc362 100644
--- a/code/R-notebook/ch11/11-colab.ipynb
+++ b/code/R-notebook/ch11/11-colab.ipynb
@@ -14,6 +14,7 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
+    "options(Ncpus = 2)\n",
     "install.packages(c(\"h2o\", \"keras\"))"
    ]
   },
diff --git a/code/R-notebook/ch12/12-colab.ipynb b/code/R-notebook/ch12/12-colab.ipynb
index 447fd37..69cb893 100644
--- a/code/R-notebook/ch12/12-colab.ipynb
+++ b/code/R-notebook/ch12/12-colab.ipynb
@@ -14,7 +14,8 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
-    "system(\"sudo apt install -y libcurl4-openssl-dev libv8-dev r-cran-rcppeigen\")\n",
+    "system(\"apt-get install -y libcurl4-openssl-dev libv8-dev r-cran-rcppeigen\")\n",
+    "options(Ncpus = 2)\n",
     "install.packages(c(\"caret\", \"fable\", \"feasts\", \"prophet\", \"tsibble\", \"urca\"))"
    ]
   },
diff --git a/code/R-notebook/ch13/13-colab.ipynb b/code/R-notebook/ch13/13-colab.ipynb
index 30ae416..e848959 100644
--- a/code/R-notebook/ch13/13-colab.ipynb
+++ b/code/R-notebook/ch13/13-colab.ipynb
@@ -14,6 +14,7 @@
    "outputs": [],
    "source": [
     "# Google Colaboratoryの環境設定\n",
+    "options(Ncpus = 2)\n",
     "install.packages(c(\"factoextra\", \"gplots\", \"igraph\"))\n",
     "devtools::install_github(\"vqv/ggbiplot\")"
    ]