Buttons to add/delete rows and reset a matrix input.
Examples
matrixButtonGroup("matrix")
#> <div class="row">
#> <div class="col-sm-4">
#> <button class="btn btn-default action-button btn btn-block btn-outline-primary" id="btn_matrix_addrow" style="width:100%;" type="button"><span class="action-icon"><i class="fas fa-plus" role="presentation" aria-label="plus icon"></i></span><span class="action-label"></span></button>
#> </div>
#> <div class="col-sm-4">
#> <button class="btn btn-default action-button btn btn-block btn-outline-primary" id="btn_matrix_delrow" style="width:100%;" type="button"><span class="action-icon"><i class="fas fa-minus" role="presentation" aria-label="minus icon"></i></span><span class="action-label"></span></button>
#> </div>
#> <div class="col-sm-4">
#> <button class="btn btn-default action-button btn btn-block btn-outline-primary" id="btn_matrix_reset" style="width:100%;" type="button"><span class="action-icon"><i class="fas fa-arrow-rotate-left" role="presentation" aria-label="arrow-rotate-left icon"></i></span><span class="action-label"></span></button>
#> </div>
#> </div>
