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<p>Yes, you need point data to start from, but then vectors can
bei/are generated from the attributes you mentioned.</p>
<p>Andreas<br>
</p>
<div class="moz-cite-prefix">Am 13.11.20 um 11:47 schrieb L.W.:<br>
</div>
<blockquote type="cite"
cite="mid:cd1f5b7c-4703-530f-d5b7-b51caa5632d5@gmx.de">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<p>from the docs ...</p>
<p>****It can only be used to render point data****</p>
<h4 style="box-sizing: border-box; margin-top: 0px; font-weight:
700; font-family: "Roboto Slab", ff-tisa-web-pro,
Georgia, Arial, sans-serif; font-size: 18.4px; color: rgb(64,
64, 64); font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; letter-spacing: normal; orphans: 2;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: 2; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(252, 252,
252); text-decoration-style: initial; text-decoration-color:
initial;"><a class="toc-backref"
href="https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#id15"
style="box-sizing: border-box; color: rgb(64, 64, 64);
text-decoration: none; cursor: pointer; outline-width: 0px
!important; user-select: auto !important;"
moz-do-not-send="true"><span class="section-number"
style="box-sizing: border-box;">12.2.2.2.6.<span> </span></span>The
Vector Field Marker</a></h4>
<p class="" style="box-sizing: border-box; line-height: 24px;
font-size: 16px; margin: 0px 0px 24px; color: rgb(64, 64, 64);
font-family: Lato, proxima-nova, "Helvetica Neue",
Arial, sans-serif; font-style: normal; font-variant-ligatures:
normal; font-variant-caps: normal; font-weight: 400;
letter-spacing: normal; orphans: 2; text-align: start;
text-indent: 0px; text-transform: none; white-space: normal;
widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;">The vector field
marker is used to display vector field data such as earth
deformation, tidal flows, and the like. It displays the vectors
as lines (preferably arrows) that are scaled and oriented
according to selected attributes of data points. ****It can only
be used to render point data****; line and polygon layers are
not drawn by this symbology.</p>
<p style="box-sizing: border-box; line-height: 24px; font-size:
16px; margin: 0px 0px 24px; color: rgb(64, 64, 64); font-family:
Lato, proxima-nova, "Helvetica Neue", Arial,
sans-serif; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-weight: 400; letter-spacing:
normal; orphans: 2; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;">The vector field is
defined by attributes in the data, which can represent the field
either by:</p>
<ul class="simple" style="box-sizing: border-box; margin: 0px 0px
24px; padding: 0px; list-style: disc; line-height: 24px; color:
rgb(64, 64, 64); font-family: Lato, proxima-nova,
"Helvetica Neue", Arial, sans-serif; font-size: 16px;
font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-weight: 400; letter-spacing:
normal; orphans: 2; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;">
<li style="box-sizing: border-box; list-style: disc;
margin-left: 24px;">
<p style="box-sizing: border-box; line-height: 24px;
font-size: 16px; margin: 0px;"><strong style="box-sizing:
border-box; font-weight: 700;">cartesian</strong><span> </span>components
(<code class="docutils literal notranslate"
style="box-sizing: border-box; font-family:
SFMono-Regular, Menlo, Monaco, Consolas, "Liberation
Mono", "Courier New", Courier, monospace;
font-size: 12px; white-space: nowrap; max-width: 100%;
background: rgb(255, 255, 255); border: 1px solid rgb(225,
228, 229); padding: 2px 5px; color: rgb(231, 76, 60);
overflow-x: auto;"><span class="pre" style="box-sizing:
border-box;">x</span></code><span> </span>and<span> </span><code
class="docutils literal notranslate" style="box-sizing:
border-box; font-family: SFMono-Regular, Menlo, Monaco,
Consolas, "Liberation Mono", "Courier
New", Courier, monospace; font-size: 12px;
white-space: nowrap; max-width: 100%; background: rgb(255,
255, 255); border: 1px solid rgb(225, 228, 229); padding:
2px 5px; color: rgb(231, 76, 60); overflow-x: auto;"><span
class="pre" style="box-sizing: border-box;">y</span></code><span> </span>components
of the field)</p>
</li>
<li style="box-sizing: border-box; list-style: disc;
margin-left: 24px;">
<p style="box-sizing: border-box; line-height: 24px;
font-size: 16px; margin: 0px;">or<span> </span><strong
style="box-sizing: border-box; font-weight: 700;">polar</strong><span> </span>coordinates:
in this case, attributes define<span> </span><code
class="docutils literal notranslate" style="box-sizing:
border-box; font-family: SFMono-Regular, Menlo, Monaco,
Consolas, "Liberation Mono", "Courier
New", Courier, monospace; font-size: 12px;
white-space: nowrap; max-width: 100%; background: rgb(255,
255, 255); border: 1px solid rgb(225, 228, 229); padding:
2px 5px; color: rgb(231, 76, 60); overflow-x: auto;"><span
class="pre" style="box-sizing: border-box;">Length</span></code><span> </span>and<span> </span><code
class="docutils literal notranslate" style="box-sizing:
border-box; font-family: SFMono-Regular, Menlo, Monaco,
Consolas, "Liberation Mono", "Courier
New", Courier, monospace; font-size: 12px;
white-space: nowrap; max-width: 100%; background: rgb(255,
255, 255); border: 1px solid rgb(225, 228, 229); padding:
2px 5px; color: rgb(231, 76, 60); overflow-x: auto;"><span
class="pre" style="box-sizing: border-box;">Angle</span></code>.
The angle may be measured either clockwise from north, or
Counterclockwise from east, and may be either in degrees or
radians.</p>
</li>
<li style="box-sizing: border-box; list-style: disc;
margin-left: 24px;">
<p style="box-sizing: border-box; line-height: 24px;
font-size: 16px; margin: 0px;">or as<span> </span><strong
style="box-sizing: border-box; font-weight: 700;">height
only</strong><span> </span>data, which displays a vertical
arrow scaled using an attribute of the data. This is
appropriate for displaying the vertical component of
deformation, for example.</p>
</li>
</ul>
<p style="box-sizing: border-box; line-height: 24px; font-size:
16px; margin: 0px 0px 24px; color: rgb(64, 64, 64); font-family:
Lato, proxima-nova, "Helvetica Neue", Arial,
sans-serif; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-weight: 400; letter-spacing:
normal; orphans: 2; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;">The magnitude of field</p>
<p style="box-sizing: border-box; line-height: 24px; font-size:
16px; margin: 0px 0px 24px; color: rgb(64, 64, 64); font-family:
Lato, proxima-nova, "Helvetica Neue", Arial,
sans-serif; font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-weight: 400; letter-spacing:
normal; orphans: 2; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(252, 252, 252); text-decoration-style:
initial; text-decoration-color: initial;"><br>
</p>
<div class="moz-cite-prefix">Am 13.11.2020 um 11:34 schrieb
Andreas Neumann:<br>
</div>
<blockquote type="cite"
cite="mid:9d5955ce-6f3b-14ba-b27c-5f409d3382cd@carto.net">Or
even easier: use the "Vector Field Marker": <br>
<br>
<a class="moz-txt-link-freetext"
href="https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#the-vector-field-marker"
moz-do-not-send="true">https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#the-vector-field-marker</a>
<br>
<br>
Am 13.11.20 um 11:33 schrieb Andreas Neumann: <br>
<blockquote type="cite">Hi, <br>
<br>
Yes - you can use Geometry Generators for that. Use the
make_point() and make_line() expressions for that. <br>
<br>
See
<a class="moz-txt-link-freetext"
href="https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?highlight=geometry%20generator#the-geometry-generator"
moz-do-not-send="true">https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?highlight=geometry%20generator#the-geometry-generator</a><br>
<br>
Greetings, <br>
Andreas <br>
<br>
Am 13.11.20 um 11:26 schrieb L.W.: <br>
<blockquote type="cite">Hi, <br>
<br>
is it possible to draw automatically a line between two
points defined <br>
by 4 fields (x1,y1 - x2,y2) in an attributetable? <br>
<br>
but I do not want to add a line-layer based on this table
nor want to <br>
draw the line by hand. <br>
<br>
thanks <br>
<br>
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