import json


def init_chart_data(number_of_channels, number_of_samples):
    """
    Initializes the chart with the specified number of samples.

    Args:
        number_of_channels (int): The number of channels to be displayed.
        number_of_samples (int): The number of samples to be displayed.

    Returns:
        str: A string representation of a JSON object containing the chart data.
    """
    samples = []
    for i in range(number_of_samples):
        samples.append(i)
    data = []
    for _ in range(number_of_channels):
        data.append([None]*number_of_samples)

    chart_data = {'data': data, 'samples': samples, 'sample_count': 0}

    return json.dumps(chart_data)