Several questions problems about chart widget

How-to
1

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Description

I have several questions about using chart widget

  1. If I add 4 series to a chart, how to hide one or more series in some case?
  2. In the docs example lv_example_chart_5, how to show the x axis value of pressed points?
  3. In the lv_example_chart_6 has an API called lv_obj_draw_part_check_type, but I didn’t found it in version 8.0.1? Is it a mistake?

What MCU/Processor/Board and compiler are you using?

What LVGL version are you using?

8.0.1

What do you want to achieve?

What have you tried so far?

Code to reproduce

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2

You can use lv_chart_hide_series(chart, series, true);.

See this as an example:
Examples — LVGL documentation

It was introduced for v8.1.0 so it’s in master. I suggest updating LVGL from the master branch.

3

As for the second question, in lv_example_chart_5 I display 1000 data with zoom, then I want to show the x axis ,range from 1~1000, and I add some codes in the examples

lv_chart_set_range(chart, LV_CHART_AXIS_PRIMARY_X, 1, 1000);
lv_chart_set_axis_tick(chart, LV_CHART_AXIS_PRIMARY_X, 10, 5, 20, 2, true, 50);

but it seems still show the range 0~19 in the x axis.

4

Another quesion, in lv_example_chart_4 it can show the value of the point, I combine this example with lv_example_chart_5(it mean display 1000 points and can show the pressed point value), now I want to show the x axis when I pressed one point, so I add some codes

  lv_coord_t* x_array = lv_chart_get_x_array(chart, ser);
 lv_coord_t value_x = x_array[id];

lv_snprintf(buf, sizeof(buf), LV_SYMBOL_DUMMY"%d, %d", value_x, value_y);

and found it value_x is wrong, it shows an error numbur, can u tell me how it happens? Is there something I miss?

5

I know, lv_chart_get_x_array need the point array in x axis, but I add the series to the y array.
So, I should printf id instead of value_x

6

The X range can be used on with SCATTER chart type. Try this:

lv_snprintf(buf, sizeof(buf), LV_SYMBOL_DUMMY"%d, %d", id, value_y);

Yes :slight_smile:

7

Thanks, I tried lv_chart_set_type(chart, LV_CHART_TYPE_SCATTER)，the line becomes wired and the chart_event_cb seems can’t show the pressed point value.

8

Why do you use a scatter chart? Scatter chart allows setting both the x and y value. See here.

It seemed to me you need a simple line chart.

9

I need to show a large points chart(most 30000 data points)

10

The line chart is fine for that.

11

Yes, so if I used the line chart to show 30000 datas, and I use the zoom effect, then how to set X axis to show the range from 1~30000 while the chart is zooming

12

Ah, I see. So want to keep the div lines and axis ticks not zoomed, right?

13

The fact is , based on the code of lv_example_chart_5, I add the Y axis tick by lv_chart_set_axis_tick(), it shows the Y axis tick well. Then I add the X axis tick by lv_chart_set_axis_tick(chart, LV_CHART_AXIS_PRIMARY_X, 10, 5, 20, 2, true, 50), the number of major ticks on the axis is 20, so the expected tick labels should be “0, 1500, 3000 …”， for I set the range is (0, 30000), but in fact it shows 0, 1, 2, …19, it seems it’s worthless by set X axis tick in the lv_example_chart_5

14

It because you set 20 major ticks.

It sets 100:

    lv_chart_set_axis_tick(chart, LV_CHART_AXIS_PRIMARY_X, 10, 5, 100, 2, true, 50);

Probably you should set it dynamically based on the zoom level.