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Signature Description Parameters 
#include <DataFrame/DataFrameTransformVisitors.h>

template<typename T, typename I = unsigned long>
struct ClipVisitor;
This is a transformer visitor. It means the column(s) passed to this visitor is not read-only and its values may change

This visitor sets any column value greater than upper to upper and any value smaller than lower to lower.

This works with both scalar and multidimensional (i.e. vector and arrays) datasets.

get_result() returns the number of items changed.
ClipVisitor(const T &upper, const T &lower)
T: Column data type
I: Index type 
static void test_ClipVisitor()  {

    std::cout << "\nTesting ClipVisitor{ } ..." << std::endl;

    MyDataFrame df;

    StlVecType<unsigned long>  idxvec = { 1UL, 2UL, 3UL, 10UL, 5UL, 7UL, 8UL, 12UL, 9UL, 12UL, 10UL, 13UL, 10UL, 15UL, 14UL };
    StlVecType<double>         dblvec = { 0.0, 15.0, 14.0, 15.0, 1.0, 12.0, 11.0, 8.0, 15.0, 6.0, std::numeric_limits<double>::quiet_NaN(), 4.0, 14.0, 14.0, 20.0 };
    StlVecType<int>            intvec = { 1, 2, 3, 4, 5, 8, 6, 7, 11, 14, 9 };
    StlVecType<std::string>    strvec = { "zz", "bb", "zz", "ww", "ee", "ff", "gg", "zz", "ii", "jj", "kk", "ll", "mm", "ee", "" };

    df.load_data(std::move(idxvec),
                 std::make_pair("dbl_col", dblvec),
                 std::make_pair("str_col", strvec));
    df.load_column("int_col", std::move(intvec), nan_policy::dont_pad_with_nans);

    const double        upper { 14 };
    const double        lower { 5 };
    ClipVisitor<double> clip { upper, lower };
    auto                result { df.visit<double>("dbl_col", clip).get_result() };

    assert(result == 7);
    assert(df.get_column<double>("dbl_col")[0] == 5.0);
    assert(df.get_column<double>("dbl_col")[1] == 14.0);
    assert(df.get_column<double>("dbl_col")[2] == 14.0);
    assert(df.get_column<double>("dbl_col")[4] == 5.0);
    assert(df.get_column<double>("dbl_col")[5] == 12.0);

    // Now multidimensional data
    //
    constexpr std::size_t   dim { 3 };

    using ary_col_t = std::array<double, dim>;
    using vec_col_t = std::vector<double>;

    StlVecType<ary_col_t>   ary_md  {
        { 1.0, 2.0, 3.0 }, { 10.0, 3.0, 0.2 }, { 3.0, 1.0, 4.0 }, { 4.0, 2.5, 2.0 }, { 0.18, 12.0, 1.0 }, { 5.0, 1.5, 3.5 },
        { 2.5, 3.5, 2.5 }, { 3.5, 2.0, 1.0 }, { 1.0, 40.0, 4.5 }, { 0.2, 3.0, 2.0 },
    };
    StlVecType<vec_col_t>   vec_md  {
        { 1.0, 2.0, 3.0 }, { 10.0, 3.0, 0.2 }, { 3.0, 1.0, 4.0 }, { 4.0, 2.5, 2.0 }, { 0.18, 12.0, 1.0 }, { 5.0, 1.5, 3.5 },
        { 2.5, 3.5, 2.5 }, { 3.5, 2.0, 1.0 }, { 1.0, 40.0, 4.5 }, { 0.2, 3.0, 2.0 },
    };

    df.load_column<ary_col_t>("ARY MD", std::move(ary_md), nan_policy::dont_pad_with_nans);
    df.load_column<vec_col_t>("VEC MD", std::move(vec_md), nan_policy::dont_pad_with_nans);

    const vec_col_t         vec_upper = { 9.9, 10.0, 3.0 };
    const vec_col_t         vec_lower = { 0.8, 0.5, 0.99 };
    const ary_col_t         ary_upper = { 9.9, 10.0, 3.0 };
    const ary_col_t         ary_lower = { 0.8, 0.5, 0.99 };
    ClipVisitor<vec_col_t>  vec_clip {vec_upper, vec_lower};
    ClipVisitor<ary_col_t>  ary_clip {ary_upper, ary_lower};

    df.single_act_visit<vec_col_t>("VEC MD", vec_clip);
    df.visit<ary_col_t>("ARY MD", ary_clip);

    const auto  &vec_md_ref { df.get_column<vec_col_t>("VEC MD") };
    const auto  &ary_md_ref { df.get_column<ary_col_t>("ARY MD") };

    assert(vec_clip.get_result() == 9);
    assert(ary_clip.get_result() == 9);
    assert(vec_md_ref.size() == 10);
    assert(ary_md_ref.size() == 10);

    assert(vec_md_ref[0][0] == 1.0);
    assert(vec_md_ref[0][1] == 2.0);
    assert(vec_md_ref[0][2] == 3.0);
    assert(vec_md_ref[1][0] == 9.9);
    assert(vec_md_ref[1][1] == 3.0);
    assert(vec_md_ref[1][2] == 0.99);
    assert(vec_md_ref[4][0] == 0.8);
    assert(vec_md_ref[4][1] == 10.0);
    assert(vec_md_ref[4][2] == 1.0);
    assert(vec_md_ref[9][0] == 0.8);
    assert(vec_md_ref[9][1] == 3.0);
    assert(vec_md_ref[9][2] == 2.0);
    assert(ary_md_ref[0][0] == 1.0);
    assert(ary_md_ref[0][1] == 2.0);
    assert(ary_md_ref[0][2] == 3.0);
    assert(ary_md_ref[1][0] == 9.9);
    assert(ary_md_ref[1][1] == 3.0);
    assert(ary_md_ref[1][2] == 0.99);
    assert(ary_md_ref[4][0] == 0.8);
    assert(ary_md_ref[4][1] == 10.0);
    assert(ary_md_ref[4][2] == 1.0);
    assert(ary_md_ref[9][0] == 0.8);
    assert(ary_md_ref[9][1] == 3.0);
    assert(ary_md_ref[9][2] == 2.0);
}

C++ DataFrame