@bokeh/bokehjs/build/js/lib/models/scales/log_scale.js

Interactive, novel data visualization

import { ContinuousScale } from "./continuous_scale";
export class LogScale extends ContinuousScale {
    static __name__ = "LogScale";
    constructor(attrs) {
        super(attrs);
    }
    get s_compute() {
        const [factor, offset, inter_factor, inter_offset] = this._compute_state();
        return (x) => {
            if (inter_factor == 0) {
                return 0;
            }
            else {
                const _x = (Math.log(x) - inter_offset) / inter_factor;
                return isFinite(_x) ? _x * factor + offset : NaN;
            }
        };
    }
    get s_invert() {
        const [factor, offset, inter_factor, inter_offset] = this._compute_state();
        return (xprime) => {
            const value = (xprime - offset) / factor;
            return Math.exp(inter_factor * value + inter_offset);
        };
    }
    _get_safe_factor(orig_start, orig_end) {
        let start = orig_start < 0 ? 0 : orig_start;
        let end = orig_end < 0 ? 0 : orig_end;
        if (start == end) {
            if (start == 0) {
                [start, end] = [1, 10];
            }
            else {
                const log_val = Math.log10(start);
                start = 10 ** Math.floor(log_val);
                if (Math.ceil(log_val) != Math.floor(log_val)) {
                    end = 10 ** Math.ceil(log_val);
                }
                else {
                    end = 10 ** (Math.ceil(log_val) + 1);
                }
            }
        }
        return [start, end];
    }
    /*protected*/ _compute_state() {
        const source_start = this.source_range.start;
        const source_end = this.source_range.end;
        const target_start = this.target_range.start;
        const target_end = this.target_range.end;
        const screen_range = target_end - target_start;
        const [start, end] = this._get_safe_factor(source_start, source_end);
        let inter_factor;
        let inter_offset;
        if (start == 0) {
            inter_factor = Math.log(end);
            inter_offset = 0;
        }
        else {
            inter_factor = Math.log(end / start);
            inter_offset = Math.log(start);
        }
        const factor = screen_range;
        const offset = target_start;
        return [factor, offset, inter_factor, inter_offset];
    }
}
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